Armin Arlert

"As a soldier, I vowed long ago to dedicate my heart to the recovery of the human race! If my life ends while keeping that vow, I have no complaints!"

- Armin offers up his heart

Armin Arlert (アルミン・アルレルト) is a holder of the power of the Titans and an elite soldier in the Survey Corps. He is also a childhood friend of Eren Yeager and Mikasa Ackerman, and is one of the two deuteragonists of the series. Although he appears to be the physically weakest of the 104th Training Corps, his intelligence and strategic genius make him an invaluable asset, especially when paired with Hange Zoë's mind. After the battle of Shiganshina District, he is the current Colossus Titan.

Human Form
Armin is rather short for his age, though he has a somewhat muscular build. He has a round feminine face, blond hair that is cut in the style of a bob, large, expressive hazel eyes, brown eyebrows, and a slightly upturned nose.

In his childhood, Armin wore a long-sleeved single-buttoned jacket with a collared shirt, long dress-pants, and dress shoes. As a member of the 104th Training Corps, Armin wears the standard 104th Training Corps uniform with a white button up underneath.

Armin is part of the Survey Corps, and dresses in the standard Survey Corps uniform. Underneath his short brown jacket, he wears a white, collared button-up shirt, similar to the one he wore as an adolescent. Like his fellow comrades, Armin has supplemented his attire with a large green cape when participating in the expeditions outside the Walls. He also has long brown boots that reach up almost to his knees.

Titan Form
While his Titan form has not yet been seen, Zeke Yeager theorizes that the traits of the Colossus Titan have been passed down to Armin, albeit with a much more gaunt body than the Colossus inherited by Bertolt Hoover, though it could have been due to steam emission.

Before inheriting the power of the Colossus Titan from Bertolt, Armin's mindless Titan form shared a number of traits with its human form. It had blond, shoulder-length hair, a relatively small body with a lipless mouth and black eyes as well as a skeletal nose. While its exact height was unknown, it was shown to be big enough to peer over a three-storied rooftop and was able to eat a human whole.

Personality
Even when he was young, the naturally curious Armin had a deep fascination with the world beyond the Walls. As a child, he found and studied an illegal book about the outside world that was owned by his grandfather. He told Eren Yeager, his best friend, about the book and the information that was it contained. Armin was branded a heretic by other children for his unusual interest in the outside world, and was thus frequently picked on. Too timid to defend himself, Armin would often rely on his friends Eren and Mikasa Ackerman to protect him from local bullies. This, coupled with his frail physique, was a source of much shame for Armin, leading him to have poor self-esteem and to believe that he was a burden to others. Because of this, Armin has always been very eager to prove his worth. As a child, he hoped that one day he would be able to consider himself a true equal to his friends.

When Armin got older he enrolled in military training and after graduating he joined the Survey Corps with Eren and Mikasa. He enrolled in military training and later joined the Survey Corps for his own reasons. He wanted, first, to try to make a good and meaningful impact on the world, and second, to realize his dream to see the outside world. His curiosity has remained a strong personality trait from when he was young, driving him to do whatever it takes to ensure humanity's triumph over the Titans.

Armin continued to have low self-esteem during his training years and for a short while after graduation. During this time Armin considered himself to be useless due to his lack of physical strength and skill. However, soon after graduation, he came to learn that his mind is an equally valuable asset to the military, and that he can use his brain to help people. Consequently, Armin gradually gains confidence in himself and his abilities. Nonetheless, he can still be hard on himself at times. The fact that he is so willing to sacrifice himself to achieve a goal shows that he still does not value his own life as much as he should.

Armin is exceptionally loyal and selfless. He constantly worries for the safety of his friends. He is always prepared to throw himself into dangerous situations to save them, even offering to sacrifice himself for Mikasa. When he, Jean Kirstein, and Reiner Braun had to decide who would be left behind without a horse, Armin immediately offered himself without hesitation. When Jean was injured in battle, Armin rushed to his aid, placing himself in danger as well. Although he and Eren were determined to realize their dream of seeing the outside world, Armin was content to give his life in order to defeat the Colossus Titan and to have his dream fulfilled through Eren. Armin is also very level-headed, keeping Eren and Mikasa under control whenever their emotions get the better of them. He has talked down a fight Eren started with a soldier, and restrained Mikasa from acting rashly during Eren's military trial.

Armin is a very analytical person. He likes to think deeply about situations and solve problems using his mind. These personality traits, in conjunction with his intelligence, good judgment, level headedness, ability to plan ahead, and ability to come up with creative ideas and think outside the box make him a great tactician.

He is not an extrovert or loud person. When he was suddenly thrown into a leadership role that involved being in the spotlight, speaking in front of people and ordering people around constantly, he got quite anxious.

Armin has shown great investment in humanity's future, and is always striving for and thinking about how he can change things for the betterment of mankind.

Armin's hard and cruel life has caused him to have certain beliefs about how the world works. Armin believes that (in the cruel world in which they live) in order to surpass monsters, accomplish goals or make a difference, you must be willing to sacrifice anything, even your humanity. Armin admires strong leaders such as Erwin Smith, Darius Zackly, Ian Dietrich, and Dot Pixis for their ability to sacrifice themselves and their humanity in order to achieve their goals. He believes that tactical decisions should be based on logic rather than emotions.

Despite the fact that Armin takes calculated tactical decisions, he is also a very emotionally sensitive and empathetic person. Due to Armin's kind heart, he faces conflict in his mind with his belief that he has to force himself to throw away his humanity. For example, Armin killed a person to save Jean as it was the logical thing to do; however, he became very emotionally upset afterwards. This, in conjunction with the fact that he is hard on himself whenever he does something wrong, means that he is yet to completely throw away his humanity. Armin's most consistent traits remain his kind heart and keen intuition, making him often concerned with the group's morality.

History
Armin originally lived in the Shiganshina District of Wall Maria with his parents and grandfather.

One day, after the latest in a series of beatings by bullies, Armin sat against a building, crying. Another boy, Eren Yeager, appeared around the corner with a shady look on his face. Eren asked Armin why he never fought back, and claimed that that was why they treated him like that; he then asked him if he wanted to be on the losing side forever. Armin then claimed that he was not losing by not running away. Eren then asked for Armin's name, and the two began a friendship.

Both Armin and Eren were united together as outcasts from the other children in town. One day, Armin discovered a book belonging to his grandfather, describing the outside world. Inspired by what he read, Armin showed the book to Eren, who was inspired by Armin's excitement to also aim to one day leave the Walls. Armin would often spend his time enthusing Eren about the outside world, for which Armin held a passionate curiosity. Reading from his grandfather's book about salty oceans, deserts and other surreal places, Armin expressed a desire to one day venture out and see these magnificent sights for himself. However, Armin's interest in the outside world was met with frequent harassment by local bullies, who regarded him as a heretic.

Fall of Shiganshina arc
In the year 845, Armin would once again find himself cornered by bullies who mock him for his deep curiosity for the outside world. Refusing to fight back, Armin would need to be rescued by the timely appearance of Eren and Mikasa. Later, he and his two friends settle by the riverbank, where Eren broods over his desire to join the Survey Corps. Just as Armin muses how the Walls can not protect humanity forever, the Colossus Titan appears and subsequently breaches Wall Maria as Armin and the others watch in horror. As Titans flood the Shiganshina District, Eren and Mikasa head back home to find their doomed mother. Armin tries to stop them, but finds himself petrified by fear. Unbeknownst to Eren and Mikasa, Armin was the one to locate and inform Hannes to save the two before they get killed by the Titans.

After escaping Shiganshina, Armin's parents were both drafted to help try to reclaim the lands lost after the fall of Wall Maria. However, they, like most who participated, were killed during the mission, and Armin was left an orphan. Despite being told that his parents were participating in a Recovery Operation, Armin knew that his parents and the other civilians had been sent on a suicide mission so that there would be fewer mouths for the government to feed. With no family left, Armin moved into a settlement with Eren until the two of them turned twelve, and were able to join the Military.

104th Training Corps arc
No longer content with sitting by in the face of the Titan threat, Armin decides to enlist into military training along with Mikasa and Eren. He was able to pass the basic aptitude test after some effort, and tried to help Eren with it when he struggled to stay upright. Although high in intellect, Armin was considered weak in physical strength, and did not graduate at the top of the class.

The night after their graduation, and before the trainees had decided on their chosen section of the military, (Military Police, Wall Garrison, or Survey Corps,) Armin sits with Eren and Mikasa to eat, and watches as Eren responds to a taunting Jean by finally deciding to set the record straight and giveing a moving speech to the whole of the 104th Training on how he wants to kill the Titans to gain freedom and pursue his dream to see the outside world.

After dinner, Armin finds Eren and Mikasa sitting outside the building and joins them, saying that the party is over and that they should head back to the dorms. Before they do, Eren asks Armin which section of the military he will be joining. Armin sits down and reveals that he will join the Scouting Legion along with Eren and Mikasa. Eren questions his choice incredulously, citing Armin's physical weaknesses. Armin affirms his worries by acknowledging that he is physically weak. Eren responds supportively but advises Armin not to follow his own crazy course of action while neglecting his own strong points. Armin responds bitterly saying that he would rather die than become a burden.

Before Eren or Mikasa can answer, they are interrupted by seeing Hannes, who they now salute as the captain of the Wall Garrison. Hannes points out that its been 5 years since he is seen them. He then mentions that he still has no idea where the missing Dr. Yeager even is, and that Eren is possibly the only one with memories as to his whereabouts and asks him of he can remember anything. Eren then collapses, worrying Hannes, Armin, and Mikasa who he tells that even though this happens to him, he is still unable to remember.

Battle of Trost District arc
Armin is shaken by the news of the Titan attack on Trost. He trembles in fear, realizing how sorely unprepared they are to respond, but Eren manages to shake him out of it. Later, Armin joins Eren's squad in the middle guard of Trost and exchanges confident words with Eren about killing Titans, and soon after departs with Mina Carolina, Thomas Wagner, Mylius Zeramuski, and Nac Tias to their assigned location. Along the way, Thomas is caught by surprise and eaten by an abnormal Titan. Enraged and vengeful, Eren charges ahead of the others to engage the Titan, and Armin and the others follow suit. However, the group is ambushed and torn apart by the surrounding Titans, leaving only Armin and Eren alive, with Eren missing his left leg. Shocked and horrified, Armin is left immobile as a nearby Titan plucks him up and attempts to swallow him. Eren, just barely conscious enough to remember how Armin inspired him to see the outside world, leaps to Armin's aid. Eren hurls Armin out of the Titan's mouth, but is eaten in his place as Armin screams in anguish.

Stuck in a state of shock for some time, Armin is shaken out of it by Connie who questions where the rest of his squad is. Armin suffers a mental breakdown, despising himself for his cowardice that resulted in Eren's death. He leaves to inform the rear guard of what happened, along the way lamenting how the world is and always has been hell. On the way, he encounters Hannah trying to resuscitate Franz. Armin tells Hannah to stop, seeing all too well that Franz is bisected and already dead.

Armin is later confronted by Mikasa above the rooftops with the other stranded trainees. She questions him about Eren's location, but as soon as Armin looks at her with tearful eyes she understands. Armin blurts out the names of all the fallen soldiers in Eren's squad, ending with Eren himself. Despite his clear regret, Mikasa calmly comforts Armin and explains that they must not get emotional at a time like this. Armin follows as Mikasa guides the leaderless trainees to safety, but realizes how she is only masking her distress. When Mikasa carelessly uses up all of her gas, Armin comes to her aid. Soon after, Armin, along with Mikasa and Connie, witness the appearance of the mysterious Titan who only kills other Titans.

With Mikasa's gas is exhausted, Armin provides her with all the remaining fuel and blades he has, seemingly ready to remain behind. Armin requests to keep one blade, implying to commit suicide with it, but Mikasa and Connie refuse to leave him behind. With Trost's military headquarters overrun with Titans, and the soldiers running low on fuel, Armin devises a plan to lure the Rogue Titan towards the HQ to wipe out the surrounding Titans. Once inside the HQ, Armin constructs a plan to eliminate the Titans infesting the supply depot inside. While Armin and several other soldiers act as bait, members of the 104th's top 10 would slay the seven Titans by jumping on them from the rafters. (They did this as they were out of gas for their vertical equipment.) Armin's strategy works, and the trainees kill all the Titans and refuel their equipment. Shortly after, Armin witnesses Eren mysteriously emerge from the Rogue Titan's nape, unconscious but alive.

After being recovered, Eren is detained by a group of soldiers whoare going to execute him. Armin and Mikasa defend him, as he wakes up surprised and confused. Eren plans to escape over the Walls unless Armin is able to convince the soldiers of Eren's value to humanity. Eren tells him that his quick thinking has saved him and Mikasa before, as he was the one who went to Hannes when Shiganshina was overrun. Armin, more confident than ever, walks into the open and tries convincing the soldiers of Eren's value in humanity's battle against the Titans, citing the many Titans Eren killed in his Titan form. As a soldier, he then passionately declares that he is ready to die for this cause and makes a grand salute. Pixis, noticing his determination and passion, prevents their execution.

Now with a boost in self-confidence, he tells the senior strategists that Eren could carry the boulder over to the hole while other soldiers could lure the Titans towards the Walls. They proceed with the plan. Later, when Eren loses control of his Titan form and knocks himself out, Armin rushes to Eren and lands on his back. Remembering the spot where Eren had risen earlier, Armin stabs into him a little askew so that it would not be fatal, but would wake him up. He reminds Eren of his personal vendetta against the Titans, but Eren only becomes responsive once he reminds him of the world beyond the Walls and asks him to think of the reason he wanted to go out there to begin with. Eren, successfully motivated by Armin's words, carries the boulder and plugs the breach. The newly returned Survey Corps the help mop up the remaining Titans in Trost.

Armin is then present as a witness to the hearing that decides Eren's fate as now-revealed Titan. The trial ends with Eren being placed in the custody of the Survey Corps' Captain Levi. He and Mikasa are then separated from Eren until they are able to join the Survey Corps.

Before the trainees are able to decide their chosen military paths, the news spreads that two captured Titans, Sonny and Bean, were slain, and Armin along with other trainees from the 104th Trainee Squad are called in for inspection. Armin, Annie, and Connie discuss which branch of the military they would join. To the surprise of Connie, Armin declares he intends to join the Survey Corps. Annie compliments Armin on his courage, but states she still wants to join the Military Police and survive. To Annie's surprise, Armin tells her she is also good person because he can tell she does not want them to join the Survey Corps either. She disagrees saying that she is not a good person, because she just wants to assure her own survival by joining the Military Police.

The Female Titan arc
After joining the Survey Corps with Eren, Mikasa and the rest of the 104th's top 10 (excluding Annie Leonhart), Armin participates in the Survey Corps' 57th expedition, venturing beyond Wall Rose. Not long into the expedition, Armin's squad encounters the Female Titan, which is seemingly highly intelligent and has considerable knowledgeable about the Military's formation. The Female Titan kills Armin's entire squad, but spares Armin's life after carefully removing his hood and observing his face. As the Female Titan moves on, Reiner and Jean meet up with Armin and the three pursue the mysterious Titan. Armin suggests the Female Titan, like Eren, is a human-controlled Titan and is likely hunting for Eren. The three attempt to engage the Female Titan and Armin is thrown off his horse, but, yet again, the Female Titan does not kill him. The three manage to distract her for a while, though she immediately make a beeline for Eren's a position after warding Armin's group off.

Though they survived the encounter, Armin, Jean and Reiner are left stranded with only one horse, which is only strong enough to carry two at a time. While Reiner is patching Armin up he thinks about the Female Titan sparing him a second time and, given her resemblance and what she appears to know, Armin suspected the Female Titan may be Annie though he keeps this to himself. After being bandaged up by Reiner, Armin offers to stay behind, but luckily Krista quickly arrives with two spare horses in tow.

Reaching the Titan Forest, Armin and his fellow soldiers perch on its many high branches, distracting Titans while Erwin confronts the Female Titan. While they wait, Armin concludes that Erwin withheld vital information from most of the soldiers out of fear of traitors lurking among them. Jean criticizes his commander's actions, but Armin defends Erwin, stating that playing it safe will not bring about change. When the expedition ultimately ends in failure, Armin safely returns to Wall Rose with the remainder of the Survey Corps.

Some time later, in Stohess District, Armin locates and asks Annie, now a Military Police member, for her help in hiding Eren; they need to flee Wall Sheena to avoid Eren's inevitable execution, and they will need a MP on their side to get through the checkpoints. Although initially hesitant, Annie accepts, and Armin explains that they must smuggle Eren out of Wall Sheena by foot, taking an underground route. As he, Eren and Mikasa enter the underground tunnel, Annie refuses to follow, realizing that Armin has led her into a trap. Armin confronts Annie, asking her why she was in possession of Marco Bott's vertical equipment during equipment inspection. Annie claims that she simply found it, but then admits to have killed the two captured Titans using her own equipment when Armin accuses her of such. Annie questions why Armin did not take action if he was already so suspicious of her, but Armin states he simply could not believe it, and questions why Annie chose to not kill him when she had the chance. Annie is not sure herself, but congratulates Armin on managing to corner her, confirming her identity as the Female Titan.

Armin fires a sound grenade, signalling hidden soldiers to restrain Annie. Despite their efforts, Annie succeeds in injuring herself using a barb hidden in her father's ring, allowing her to transform. Anticipating this, Mikasa grabs both Eren and Armin and takes them further underground as Annie in her Titan form attempts to grab them. Seeing that his strategy has failed, Armin initiates plan B, trying to encourage Eren to fight Annie. Eren tries repeatedly to assume his Titan form, but cannot do so due to his reluctance to fight a friend. Having no other option, Armin suggests he and Mikasa distract Annie so that Eren may safely flee. Realizing that if he does not fight, his friends will surely die, Eren finally transforms into a Titan and fights Annie.

After realizing that she is fighting a losing battle with Eren and the Survey Corps, Annie decides to make her escape by climbing over the Wall. As Mikasa, Hange and, other Survey Corps scramble to catch up to her, Armin realizes that they will not be fast enough and instructs Eren in his Titan form to propel Mikasa up the Wall, so that she can gain enough speed to overtake Annie. Mikasa cuts off the Female's Titan's fingers and Eren pins her to the ground, allowing the other Survey Corps members to extract Annie from the nape of her Titan. When Eren emerges from his Titan form and asks about Annie's fate, Armin informs him that no one knows. He shows him that Annie encased herself in rock hard crystal upon being pulled out of her Titan.

As Eren rehabilitates, Armin takes a moment to rest with the others. Armin informs Jean that Eren's summons to the King were cancelled and that Annie is indeed the Female Titan. She is being detained underground after encasing herself in a crystal to avoid interrogation. Reflecting on the mysterious Titans found in the Walls, Armin observes that for all these years they were being protected from the Titans by Titans. Armin cannot fathom how the Walls were built in the first place, but hypothesizes that abilities like Annie's hardening power were somehow employed.

Armin's hypothesis is later confirmed when the rock sample Squad Leader Hange Zoë had picked up from Annie's Titan body matched the properties of the Walls. With this information in mind, Armin and Hange propose a way to repair Wall Maria: Eren use his own hardening ability to mend the breach. Minister Nick informs the group about a girl in the Survey Corps who may know more about the Walls, stating that while he cannot share any more details, she can. Armin and the others immediately recognize the girl in question to be Krista Lenz.

Clash of the Titans arc
Rescuing Krista, Reiner, Bertolt, Connie and a grievously injured Ymir from Utgard Castle, Armin and the Survey Corps regroup on top Wall Rose. However, Armin shortly after learns of Reiner and Bertolt's secret correspondence with Annie, confirming his and Hange's suspicion that the two are also spies. As Reiner and Bertolt attempt to take possession of Eren, they are attacked and nearly killed by Mikasa, but survive. A horrified Armin is present to witness Reiner and Bertolt's Titan transformations, marking the second and third appearance of the Armored and Colossus Titans, respectively.

Armin is called by Hange to aid Eren as he battles Reiner in his Titan form. Meanwhile the Colossus Titan is kept busy defending himself from the rest of the Corps. Advising Eren to retreat to the Wall, Armin provides Mikasa with his spare blades to support Eren against the Armored Titan. Armin and Hange put their heads together and realize that, in order to move, the area behind the Armored Titan's knees will be unprotected. They thus advise Mikasa to cripple the Armored Titan's knees, allowing Eren to gain the upper hand. However, just as the battle turns in Eren's favor, the Armored Titan lets out a loud wail, signalling Bertolt, who then proceeds to push himself off of Wall Rose and crash down on Eren and Reiner below.

Reiner and Bertolt succeed in kidnapping Eren and Ymir in the chaos, and Armin informs Mikasa after she regains consciousness that five hours have already passed since then. Mikasa despairs at the news, but her and Armin's determination are revived upon hearing a rousing speech from Hannes. Joining a force comprised of Survey Corps reinforcements, Garrison and Military Police soldiers all led by Erwin, Armin and the others begin pursing Eren and his kidnappers. Before setting off, Armin implores Krista to stay within the Walls, but she insists on joining the effort.

As Armin and the others reach the Titan Forest where Reiner and Bertolt were resting, they are beset by Titans. Entering the forest with their vertical equipment, Armin's team encounters Ymir in her Titan form. Armin notices Ymir suspiciously surveying everyone and neglecting to attack anyone. His suspicions were confirmed when Ymir suddenly captures Krista and escapes, realizing that she has sided with the traitors.

Reiner transforms into his Titan form and flees the forest with Bertolt, Ymir and a restrained Eren in tow. Pursuing on horseback, Armin notes that while the Armored Titan is slow, stopping him will be difficult due to Reiner not shedding his joint armor. Eventually, Armin and his fellow trainees succeed in latching onto the Armored Titan where they implore Bertolt to surrender Eren. Just as Bertolt suffers a breakdown, Armin and the others are forced to briefly retreat when Erwin charges into the fray, followed by a horde of Titans.

The mass of Titans behind Erwin attack the Armored Titan, slowing him down to a crawl, and Erwin leads his forces into the chaos, seizing the opportunity to rescue Eren. Unfortunately, Erwin is bitten and carried off by a Titan along the way, but Armin remains focused on the mission and joins the second attempt to retrieve Eren. Using his equipment to climb onto the Armored Titan's head, Armin confronts Bertolt, purposefully taunting him with lies that Annie is being tortured while he and Reiner save themselves. Enraged, Bertolt charges at Armin, but is intercepted by a grievously wounded Erwin who slashes Eren off of him. With Eren secured, Erwin's forces retreat, but their escape is cut off by Reiner who tosses Titans in their way.

Armin is horrified by the risk Reiner is taking, seeing that Eren could easily be eaten. In the struggle, Eren and Mikasa are knocked from their horse, and Jean is incapacitated as he and the others rush to assist them. With nowhere to run, Armin drags Jean towards a small cluster of trees and prepares to face an advancing Titan with only one sword. He looks to Eren and Mikasa, seeing them in just as desperate a situation. The friends exchange teary-eyed glances, preparing for the end. However, Armin is saved when Eren's "Coordinate" power suddenly activates, causing the Titans to attack first the Smiling Titan and then the Armored Titan. This allows Armin to retrieve a horse, and carry a wounded Jean to safety. They retreat from the battlefield, mourning the loss of Hannes, who died in the chaos, and remembering their childhood with him.

The Uprising arc
Returning safely to Wall Rose, Jean remarks that the 104th has some luck, and Armin agrees by saying that surviving their situation proves it. As Jean wonders what happened to the Titans that were chasing them, he notices a Survey Corps member and Eren lay an injured Mikasa down on the Wall. As the Survey Corps Member begins to detail her injuries like rib fractures Mikasa insists to Eren that she is okay. Eren apologizes and Armin places his hand on Eren's shoulder in a show of support for him. Armin then notices several Survey Corps members attending to Erwin Smith, shouting his name and realizing that he is losing consciousness. As he collapses, the Military insists he be immediately taken away before Eren shouts his concern.

As the wounded are taken away, Jean attends to a shaken Connie by telling him to stand and that everything will be okay. Connie replies, saying that he cannot believe he is still alive as Rico Brzenska comforts Historia. Eren grimly remarks that he got captured again and asks how many people got injured because of him. Jean answers that they left with around 100 people and most of the Garrison were eaten due to there inexperience. He mentions that only around 40 people made it back and, of them, only about half can stand, including the Survey Corps. He concludes himself, wondering what will become of them all now. Armin tries to soften the situation, saying that they experienced no losses on the way back, with the Titans ignoring them and only attacking the Armored Titan. He mentions the Female Titan being able to draw other Titans toward itself, and asks Eren if this time it was him drawing them to the  Armored Titan. Jean, looking surprised, asks Eren if he really did control the Titans. Eren responds saying he still does not know for sure. Connie interrupts and asks him if that is true. He realizes himself that that was the reason why the Titans headed away from them, and theorizes that if everyone had kept fighting, they would have all died.

Armin continues listening in as Jean speaks to Eren once again, this time of the price they gave up to rescue him, which includes Erwin Smith losing his right arm, Mikasa having her rib cage shattered, Hannes being devoured, and 60% of the soldiers dying, and asks if he is really worth such a heavy toll. He finishes himself by saying that it all depends on Eren. Eren gives a soft laugh and informs Jean how he is become quite the preacher since he joined the Survey Corps. Jean rebuffs saying Eren is the one who is always hesitant to talk. Connie also remarks how it is weird for Jean to become so serious all of a sudden. Armin contributes, agreeing with Connie. Jean, who is clearly flustered simply tells them that he is the hero who saved Mikasa. After this, Eren thanks Jean, saying it is because of him that he no longer needs to hesitate. Eren affirms his decision to control the Titans, and seal up Wall Maria, as well as capturing the ones who kidnapped him, and making sure that the deaths of everyone are recognized as services to humanity. When Eren concludes himself, Krista attempts to stand up, as Rico and Armin try to persuade her differently. They're interrupted, as Krista reveals her true name to be Historia. She urgently tells Eren that they need to head to the Wall.

Some time later, Armin is seen helping Jean and Sasha carry food into their new relocated house. Jean tries to get Sasha to carry a box while she complains about it is weight. Jean explains that it is filled with potatoes, hinting at her earlier incident with Keith Shadis. Sasha merely brushes it off saying she forgot all about it. Jean disagrees, saying that nobody could forget that incident. Armin mentions that there is inflation all over, and if they lost their current provisions then they would surely starve. After the food is inside, Sasha asks why they bought so much food when they could just easily hunt for it in the woods. Armin reminds her that hunting is prohibited in the area.

Eren appears and reminds them all of the importance of cleaning off their shoes before coming in causing Jean to yell at him that him and remind his that he is not his mother. Mikasa and Historia come back after chopping wood, much to Armin's shock, as he tries to remind her that she is not a wild animal and should not be moving around yet. Eren comments on how he also tried to stop her but she would not listen, and was doing sit-ups. Jean then yells at Eren for daring to spy on Mikasa. Sasha speaks on how this is like all of them being trainees again. Armin is quick to remind everyone that protecting Eren and Historia is an important task. He then asks why they were selected for Levi's new squad, commenting on the fact that many veterans are still alive. Eren tells them all to finish cleaning before Levi and Connie return.

The group then reunites with Levi and discuss Armin's idea of sealing the hole in Wall Maria using Eren's Titan hardening abilities. Hange informs them that Nick was found dead that morning, tortured and murdered by members of the Military Police's First Interior Squad, and Armin wonders how much he would have revealed, though Levi guesses he did not reveal anything. He also was there when Historia told about her past, her mother's murder and the events that led to her enlistment in the Survey Corps.

During a failed test for Eren to harden his Titan form, Armin was present. He was also present when the group read Erwin's orders, looking shocked at the sight of it. During their first official operation, Armin serves as a body double for Historia, and is eventually captured by the organization that wishes to take possession of Eren and Historia. While being held captive with Jean, who was serving as Eren's double, one of the men harassed him, asking over and over to hear Armin's voice, as he was suspected to be Historia. Armin displayed great discomfort at this, being driven to tears from it.

Armin is seen still tied up with Jean as the men issued to take Eren and Krista arrive, observing them silently before they are attacked by Mikasa and Levi. He and Jean then race from their positions, revealing that they were pretending to be tied up, and tie the beaten men up.

After the men are officially detained and questioned by Levi and Mikasa, Levi orders Armin to fix the mouth gag on the man who originally harassed Armin. As he began to fix the gag, the man mentioned that he heard Armin was actually a boy. He then tells Armin that he used to be normal, but Armin now turned him into this and then tells him to do something about it. Armin appears shocked, unresponsive to the man. Jean then tells Armin to leave the work to him.

After the Survey Corps capture two First Interior Squad officers, Armin is seen with the rest of his friends talking about how they might be able to pull off a successful coup d'etat. he is present when the Survey Corps discuss the plan to make Historia ascend as queen.

After Eren and Historia are kidnapped by the First Interior Squad, he is seen at Trost district, preparing with the rest of the Survey Corps to retrieve the caskets in which Eren and Historia are being transported. It turns out to be a trap to lure the Survey Corps, and they immediately try to escape town, with Armin driving a carriage. One female member of the First Interior Squad gets through and tries to shoot Armin, but Mikasa kicks her and she lands on the carriage. She gets up, ignores Jean's threat and knocks his gun away. While she is pointing a gun at Jean, Armin reacts quickly, pulls out his own gun and shoots her in the head. Thus, he helps save Jean. After the SC retreat to safety, he was not able to take the guilt of killing another human being and becomes sick. Mikasa comforts him. Levi tells him that he cannot go back to being the way he was, as his hands are now already dirty. He later assists in baiting and capturing Marlowe Freudenberg and Hitch Dreyse. After that, he plays a role in raiding the Interior MP's headquarters.

After the successful revolution, he tags along with his group to the Reiss Chapel, wondering that if Titan abilities can be ingested, who could Eren have eaten to gain his Titan power. He plays a pivotal role in planning out their fight with the remaining Interior MP forces stationed at the chapel. The plan was to take cover under the smoke by igniting gunpowder inside barrels and also by utilizing their smoke signals, as it would be advantageous for them with their lower numbers. As Hange gets injured, he is tasked to take care of them.

He witnesses Rod's Titan form crawling out from the collapsing chapel and speculates that it is behaving more like an abnormal Titan rather than a human with the power of the Titans. He assists the Survey Corps in fighting the Titan as it tries to invade Orvud District.

Return to Shiganshina arc
Once Historia takes command as the queen, he is seen helping out at the farm for the orphans and people in need from the Underground. He and the rest of Survey Corps prepare for the upcoming mission for retaking Wall Maria and have meals together. Before they set out for the mission, he reminisces their childhood with Eren and Mikasa, and enthusiastically talks of being able to see the outside world, stating that they should start by visiting the ocean.

During the night they walk towards Shiganshina, he prompts Eren as he seems to be in fear and doubt. He implicitly reminds him of their collective dream to see the outside world, making him feel better.

Once they reach Shiganshina, he scouts around and finds the remains of a camp-fire with 3 cups and a pot that had gone cold. He, along with Erwin, reason that there were at least three enemies around and they were informed of their arrival well in advance. After this, Erwin entrusts him to command a group of soldiers to weed out the enemies in hiding. He speculates about the enemy's thought process and requests the soldiers to search around inside the Walls to find hollow spots. Sure enough, one soldier stumbles across a hollow spot and from within emerges Reiner who immediately kills him. He prepares to attack Armin, but Levi swoops down and intervenes. Armin is once again entrusted by Erwin to help direct the battlefront where they would fight the Armored Titan. He relays Erwin's plan to take on the Armored Titan to squad leader Hange.

As they blow Reiner's head off, he is sad that with their abilities they could not afford any negotiations. However, Reiner gives out a roar and Armin immediately realizes that it might be a signal to call Bertolt. Sure enough, a barrel is approaching them from the sky. With the Colossus Titan coming from above, Armin and the soldiers try to flee from the scene. Before charging at Bertolt, Armin reminds everyone that they should make a last attempt to negotiate with him. Bertolt shares a bitter conversation with Armin, claiming that it was he who decided to come up with malicious schemes in order to conquer humanity. Thinking fast, Armin throws Annie's name in the conversation, declaring that only Bertolt is capable of saving her from the Military Police. Bertolt coldly dismisses Armin's remarks and approaches him with his blade ready. He reveals to Armin that he saw through his plan long ago, but he just wanted to ensure that he is to kill them properly. A betrayed Armin suggests that Bertolt thinks that all humans are descendants of evil, but Bertolt coldly protests. Following that, Mikasa attacks Bertolt from behind but their fight swiftly ends with Mikasa tethering near the edge of the building they're on top of. Shortly after, Bertolt escapes to find Reiner. Armin attempts running after Bertolt, but Mikasa stops him. Armin feels an immense explosion resonating throughout the district, signifying that Bertolt has taken his Titan form.

Armin witnesses the Colossus Titan destroy the district. When Jean asks Armin for a plan, Armin advises to tire out the Colossus Titan because it cannot climb over the Wall. Jean interrupts Armin's plan, deeming it too dangerous to risk leading the Colossus Titan to the Wall due to Erwin's group being on the other side. Jean concludes that a tactical approach is the logical plan, however they have limited supplies, such as their vertical equipment. Armin realizes that this is their only chance of attack solely counting on their current manpower. Jean asks Armin for the next phase of his plan, but Armin is out of ideas and requests Jean to take over.

Following Jean's orders to reach the river, Armin climbs onto Eren, who stays out of sight from the Colossus Titan. Jean tells Armin that he might be able to get a grasp of their situation, however in the end he would have to rely on Armin's planning for it to work. Armin, incredibly frantic, is reprimanded by Jean to stop. He is tasked to observe the Colossus Titan from the farther back while Eren attacks him to keep him from reaching the Wall.

Eren is kicked to the top of the Wall by the Colossus Titan. The Colossus Titan releases a burst of steam and Armin notices that Mikasa is hurt. She asks him if he came up with any other ideas but he has not. Before they can come up with any other plans, the group is in shock to find the Armored Titan newly transformed. After long observation and consideration, Armin finally comes up with a plan; noticing that the Colossus Titan is thinner, its energy must drain faster than a 15 meter. Armin tells Jean and Mikasa to go after the Armored Titan, while he and Eren will take the Colossus. Reminiscing the days when he and Eren promised each other that they would one day see the ocean, Armin comments that if this plan fails, he will never get to see it. Armin then stabs Eren's Titan form, telling him to wake up. Armin succeeds in waking Eren, telling him to go through with the plan no matter what. Eren hesitantly agrees.

In accordance with Armin's plan, Eren lets his Titan form fall to the ground in front of the north gate, seemingly defeated. Armin stays on the Wall, pretending to be surprised. As Eren's Titan form falls he secretly hardens his body and escapes through the nape, fleeing from the scene. Armin stays put, thinking about how Eren will carry out his dreams to see the ocean if this plan takes too long. Grappling to the Colossus Titan's teeth, Armin succeeds in getting Bertolt to emit a massive wave of heat and smoke. Armin remains grappled as the heat begins to hinder his breathing, but he remains resolute in his decision. Bertolt begins to pity Armin's selflessness and emits a massive wave of searing heat and steam to kill Armin quickly.

As Armin's flesh, skin, and clothing begin to burn off, Armin chooses to remain grappled, realizing that he is about to die and that Eren must see the ocean in his stead. Soon, Armin's grip on his sword hilt is broken, sending his charred body flying fifty meters to the rooftops below. As Bertolt inspects Eren's hardened Titan form, Eren sneaks up behind Bertolt and slices the Colossus Titan's nape, taking Bertolt alive and limbless. Eren stands on the roof by Armin's body, saying that Armin was always the bravest of his comrades.

Eren mourns Armin's sacrifice, sadly looking down upon his body. Eren then hears Armin breathing faintly and urges Levi to use the Titan serum on Armin. Levi at first agrees and then reconsiders this when Erwin is brought in. After a tense altercation with Mikasa and Eren, Levi witnessing Erwin's final moments, he decides to use the serum to save Armin and transform him into a mindless Titan. Armin's Titan form eats Bertolt who had been left behind on a rooftop for that purpose. After eating Bertolt, Armin emerges, unconscious and fully healed, having acquired Bertolt's Titan ability, and in his human form once more.

Armin has a nightmare about Bertolt but shortly after wakes up atop the Wall. When he wakes up, he notices Sasha lying next to him and discovers her severe injuries. He sees Eren heading toward him and he hugs Armin when he reaches him, relieved that he is awake. Armin is confused, so Eren informs him on the recent events that happened. After hearing this, Armin recounts the information he has been given and acknowledges that he ate Bertolt. He feels sick and asks his comrades why they did not save Erwin instead of him. Levi states that Armin should not let others regret their decision on choosing to save him, including himself. Hange claims that Armin and herself will have to prepare for whatever comes next and that they are in similar situations. Hange then says that she, Levi, Eren, and Mikasa will be heading out while Armin and the rest of the soldiers remain atop the Wall resting and keeping watch.

After their mission, Armin returns to Wall Rose with the remaining members of the Survey Corps.

Eren and Mikasa are imprisoned for having disobey to their superior and Armin stays with them. When Eren wakes up, he reminds him the reason if his presence here.

In 851, he and Eren fulfill their wish of seeing the ocean, while Eren reminds everyone of the terror lurking in the future that they will see.

Marley arc
Through the years 851 to 854, the nation of Marley sent a total of 32 scouting ships to the island of Paradis, all of which ended up missing. While the details concerning their disappearances are currently unknown, Zeke Yeager theorizes that the Eren Yeager as well as another Titan under Paradis' control, likely Armin Arlert's Colossus Titan, are responsible for the ships' disappearances.

High Intelligence
Being physically weak, Armin is rarely assigned to the front lines and rarely uses his vertical equipment for direct combat. Instead, his greatest strength lies in his intelligence - innate abilities of deduction and strategy formulation, be it in a war room or on the fly. But Armin has a keen eye for detail, making him a remarkable field tactician, a trait that distinguishes him among his fellow trainees. His strategies help save his fellow soldiers numerous times and, more remarkably, he played a key role in deducing the identities of all the hostile Titan spies among the 104th Training. Initially, Armin's intelligence was hampered by a severe lack of confidence, but after acknowledging and nurturing this side of himself, Armin's potential as a tactician began to show, and even high-ranking officers took his strategic opinions seriously.

Power of the Titans
Armin gained the power of the Titans after being injected with the Titan serum by Levi and consuming Bertolt. Like any other inheritor of the power, this grants him the ability to recover from most lethal injuries (unless his weak spot in the neck is damaged without transferring his mind to the rest of his nervous system) and to freely transform between Titan and human forms while retaining his intelligence. It is unknown if he possesses any other special ability.

Relationships

 * Eren Yeager - Eren is Armin's best friend from childhood. As children, Armin looked up to Eren, as he was always there to protect Armin from bullies regardless of the odds. It was Armin who enthused Eren about the outside world, and together the two would dream of venturing beyond the Walls. Initially, Armin felt inferior to Eren, ashamed of being in need of his protection, and lacking the courage his friend boasted. Despite this, it was Eren who gave Armin the confidence to begin using his strategic mind to its full potential, reminding him of the many times his reasoning and quick thinking have saved them. As soldiers, the two share the most powerful bond and, using their own unique abilities, had saved each other numerous times.
 * Mikasa Ackerman - Mikasa is a close friend of Armin's. Whenever Armin got into trouble with local bullies, Mikasa would come and save him. Armin looked up to Mikasa's strength and courage and felt inferior to her. Mikasa, however, believes in Armin's abilities to reason out the best solution in a dire situation and trusted him deeply. She was responsible for boosting Armin's confidence and shaping his character.
 * Jean Kirstein - While Armin was initially not that close to Jean due to the latter's rivalry with Eren, their relationship has changed considerably since joining the Survey Corps. Armin's growth as a strategist has aligned with Jean's growth as a leader, and the two often share insights or opinions with one another.
 * Annie Leonhart - The two share a mutual respect for each other, expressing admiration for each others' hidden qualities. This causes her to hesitate when attacking in her Titan form, a mistake which allowed Armin to discover her true identity. He then uses emotional blackmail in order to lure her into a trap and facilitated her eventual capture.
 * Reiner Braun - Reiner is shown to have been protective of Armin, helping him during physical training exercises and carrying him to safety during dangerous operations. Armin initially defends him when he was suspected of being a spy, but quickly realizes the truth and provides evidence of Reiner's guilt.
 * Bertolt Hoover - Armin and Bertolt interacted on few occasions, though Bertolt did consider Armin a close friend. This, of course, soured once Bertolt's true identity was revealed, and he threatened to kill Armin when the latter lied and claimed that Annie was being tortured. He was hostile toward Armin when they faced off in Shiganshina, once again coldly expressing his desire to kill him and all of his friends. He nearly made good on this threat not too long after, as he severely burned Armin with a powerful steam discharge while in his Titan form. Later when Armin was injected with the Titan serum, Bertolt's final moments were daunting, having been devoured by Armin in his mindless Titan form. Despite his crimes, it is shown that his death still haunts him, as shown in his nightmares.
 * Marco Bott - Armin noted that they were friends, and did maintenance of their equipment together. This later allowed him to recognize Marco's stolen equipment when it was presented by Annie as her own.
 * Erwin Smith - Armin held the Commander of the Survey Corps in high esteem. Although he could not always guess his superior's inner thoughts, Armin regarded him as a highly smart person and a very capable commander who was not afraid of making sacrifices to reach his goals.

People Killed

 * One unnamed member of the Military Police Brigade
 * Bertolt Hoover (as a mindless Titan)

Trivia

 * In the manga, Armin has stated that it is his grandfather, not his parents, who gave him his name.
 * The name "Armin" may have multiple meanings, either from an old German word meaning "whole", or "Herman", meaning "soldier".
 * His birthday, November 3, is celebrated in Japan as Culture Day. This holiday promotes academics, culture, and the fine arts.
 * In the side art for Volume 11, Armin, along with a few other characters, were depicted transforming into a Titan. His form had a large head that was almost the same size as his small body. This was also included in the second OVA.
 * Hajime Isayama joked in the November 2014 issue of Bessatsu Shōnen Magazine that the girl Mikasa got along with most was Armin. After much confusion, he later corrected himself and stated that Armin is in fact male.
 * Isayama has stated that Armin and Nifa are likely aware of their resemblance in looks with each other because it is often mentioned by others.
 * Armin is the only member of the current Squad Levi to not be in the top 10 graduates of the 104th Trainee Corps.

Quotes
"As a soldier, I vowed long ago to dedicate my heart to the recovery of the human race! If my life ends while keeping that vow, I have no complaints! But if you combine his “Titan Power” with our remaining military force… it might even be possible to recapture this town! For the glory of the human race, I beg you! In the moments I have left before I die! Let me explain his strategic value!"

- Armin offers up his heart.

"The people capable of changing things are the ones who can throw away everything dear to them. When forced to face down monsters, they can even leave behind their humanity. Someone who can’t throw anything away will never be able to change anything."

- Armin proclaims resolve to Jean.

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