Armin Arlert

Armin Arlert (アルミン・アルレルト) is a childhood friend of Eren's and the deuteragonist in the series. Although physically more frail than most, if not all of the current recruits, he has proven his skills as a field tactician and his above average intelligence.

Personality
Armin was very timid as a child and coupled with the fact that he was physically frail, often ended up an easy target for bullies. He was so timid that he would refuse to fight back despite being taunted to do so, always requiring Eren and Mikasa to fend for him. As such, he grew up having very low opinion of himself and thinking that he is useless. His enlisted only because his two best friends were enlisting. Despite being timid, he has a variety of traits that contrast his timid self, which began to show as he grows older and learns to appreciate his own talents and develop a higher opinion of himself. He has a big dream of wanting to venture outside the wall to see the world - a dream that he shares with Eren; he is also a loyal person who is willing to put himself in harm's way to defend a friend, shown when he was, along with Mikasa, willing to defend Eren against hostile fellow soldiers despite the very high risk of being killed; and during training, despite always on the verge of failure due to his physical frailty, he was shown to be very persistent despite the odds, refusing to give up and did his best to catch up with his friends. He was also shown during training that he has a sense of dignity when Reiner offered to carry his gear for him during a march, he refused the offer outright due to the fact that doing so would meant that he is cheating.

Story
Armin was considered the weakest and graduated below the top ten. Although his plans have saved Eren and Mikasa several times, he doesn't realize it and despises himself for being reliant on them to help him out. This occurred when they were children when he was bullied by everyone else for wanting to go outside the Walls and was considered a heretic. Armin supposively blamed himself for allowing Eren to sacrifice himself to the bearded Titan. Mikasa tells Armin that his strategies have always saved their lives and he should have more faith in himself.

Sometime later before joining the Scouting Legion, Armin suspiciously took notice of Annie in possession of Marco's Three Dimensional Maneuver Gear as her own, which he would use later on. After joining the Scouting Legion with Eren, Mikasa and the other graduates (excluding Annie Leonhardt), they were confronted by the sudden appearance of the Female Titan, seemingly very intelligent with military formation. She attacked Armin while he was wearing his hood, being under the impression that he was Eren. However, once it was removed, she realized she had the wrong subject and left him aside. It was then that Armin realized Annie was, indeed, the Female Titan.

Female Titan Arc
Armin asks Annie for her help in hiding Eren because she was in the military police and they needed her to let them pass through Wall Shina without suspicion. It worked and Armin explained that he wanted to take advantage of the geography there rather than use the 3DMG to bust through. As she was leading them to a hiding place, Annie refused to go inside to help them escape and soon asked him why he was looking at her the eyes with suspicion. Armin then took the time to ask her why she was in possession of Marco Bodt's 3DMG. He recognised it not too long ago because they would often do routine check-ups to make sure they are in pristine shape. Annie confessed that she found it after Marco died and that she did use her own 3DMG to kill the two captured titans. She then asked him that if he came to all those conclusions a long time ago, why he didn't take action then. Armin reasoned that he didn't do so because he thought there was still something wrong with his train of thought. It was when Annie refused to kill him that things turned out the way they did.

Armin attempts to capture Annie by firing the signal from his flare gun letting the townspeople capture her. As the people tried to restrain her, she managed to injure herself with a blade hidden in her father's ring. Mikasa took the time to grab both Eren and Armin and take them underground as Annie in her titan form attempts to capture them. When Armin learns his plan had failed he attempted to start plan B, tried to encourage Eren to fight Annie. Eren tried to transform into his titan form, but he was unable to do it. It was only then Mikasa and Armin learned why, he was reluctant to fight Annie again because he still couldn't believe that Annie was indeed their enemy. And he didn't want to fight against one of his comrades. Realising no other option, they prepared to take Annie on by themselves and Mikasa reminded Eren that the world is a cruel place.

Armin tells Jean Kirschtein that Eren's summonings to the King are cancelled and that Annie is the Female Titan. She's being detained underground after encasing herself in a crystal to avoid interrogation. Armin couldn't understand how the walls were built in the first place because there were no stones or bricks around. He comes to hypothesize that the titan's hardening capabilities were employed by the builders. He believes it could explain how Annie was able to encase herself in a crystal.

Armin and the others learn from Lt. Hanji that the only way they could repair the walls is if Eren can use his hardening abilities to help fix Wall Rose. Pastor Nick tells them about a girl in the Scouting Legion knowing more about what's going on and it's up to her to decide if she'll talk. Armin then recognized Christa because she was often seen with Ymir.

Breach Arc
Once the Scouting Legion has rescued the others, Armin learns that Christa's real name is Historia and how heavily injured Ymir was duing her fight with the titans. He immediately learns of Reiner and Berthold's secret correspondance with Annie. Like Mikasa, Armin was very angry to learn about their betrayal after overhearing the confession about them being responsible for Wall Maria being breached.

During the battle with Berthold, Armin states that the Colossal has very slow movements and that they should exploit it. However, they were taken by surprise when he uses his vapors of heat to keep them off him. Realising that Berthold is just as desperate to stay alive, Lt. Hanji orders Armin and the other members of the Scouting Legion to go after Reiner. Armin discovers a weak link to Reiner's line of defense when he saw his armor break. Giving Mikasa and extra set of blades, he tells her to go ofter the back of his knee caps. Soon Berthold took everyone by suprise by falling off the wall.

With Eren and Ymir now kidnapped by both him and Reiner, he focuses his attention in helping Mikasa and the others until help arrives. Armin tells her the news that she had been dreading and wrapping her lower face in the scarf, she cried. She asks him why he always has to leave them behind when trouble rises. As Armin tries to console her, Hannes arrives to give out rations to everyone in the Scouting Legion. He tells them that Eren has always been like that, running into fights despite knowing the odd are against him. Hannes even mentions that although he won't admit it, he always knew Armin and Mikasa were their to help him out. Reinvigorated and determined to rescue both Eren and Ymir, he takes his stance with the Scouting Legion, Wall Guards and Military Police. Armin warns Historia to remain out of the way, but she refuses and decides to join them.

Abilities
Being one of the physically weakest soldiers there are, he is rarely assigned to the frontlines and rarely seen using his 3DMG for fights. His main strength however, lies within his intelligence - an innate abilities in deduction and forming strategies, be it in a war room or on the fly, as well as an eye for obscure details, making him a remarkable field tactician, a trait that only he displays among the current recruits. His strategies helped save his fellow soldiers numerous times and more remarkably, he is the key person who deduced the identities of all hostile titan shifters among the current recruits. He wasn't able to display his remarkable intelligence earlier due to a serious lack of confidence in himself. After acknowledging that he is actually far more useful than he thought he is, his genius as a tactician began to show and thus far, even commanders are shown to take his opinions in matters relating to titans seriously.