Marco has short black hair which is parted in the center, freckles, and light brown eyes. He wears the standard boys uniform of the school.
A positive and optimistic student is he, Marco is known for being the peacemaker of the 1st year's class. He tolerates a lot of trouble from Jean and is a very approachable guy.
In the morning, Marco compliments Jean's new hairstyle. He later tries telling Jean that he should face reality about not being popular among girls, to his anger. When Jean's love letter turns out to be from a Titan, Marco recalls the time they encountered the Titan and Jean threw his lunch at it to escape. Sasha tries to comfort a devastated Jean by giving him food that he imagines as being two girlfriends, and Marco awaits by Jean's side for him to return to reality.
Following a challenge by the upperclassmen, Marco participates in the school's Sports Day games. When his team loses hope of winning against the upperclassmen Mikasa asks Marco if they could turn the table by taking the leaders' bandanas in the last game. Marco confirms it, before saying there is no way they can do it. Teaming up with Armin, Thomas, and Conny, Marco and his team lunge themselves at an opposing Year 2 team to save Eren's.
Following the news of an election for a new student council president, Marco believes in the great honor of working for everyone in the school as president. Jean then tells him to stop being virtuous and to say what he really thinks, asking him if it is because becoming president would mean all girls going crazy for him, assuming Marco's intention is like his. Later, all the candidates start chasing after a notebook that allegedly contains info which could help them win the election, before it is revealed it merely has cleaning tips. Marco later hands the notebook back to its owner, Ilse Langnar. After apologizing for everyone's behavior, he tells her that they are impulsive, but believes each one would make a good president.
Marco accompanies Jean on stage for the latter's final presidential speech. When the crowd boos at Jean for stating he only wants to become president for girls' attention, Marco defends Jean. He starts his speech by saying that Jean is not a strong person, so he knows what it is like to be weak, and tells the audience they would feel more comfortable with someone who can understand their point of view. Hearing this, Ilse advocates for Marco, and later his attempt to defend Jean ends up awing the audience and being elected president himself by a large margin.
In the school's 104th festival, Marco informs his class of a rotation system since their number is not enough for the two required events. He, along with Jean, Conny, Thomas, and Sasha participate in a Snow White play, while Eren and the others participate in a cheeseburgers stand. When his rotation system fails, with he and Jean nearly performing single-handedly, Marco heads to the chee-burgs stand and finds it had become popular, seeing a long line of customers. He later flees when Titans appear and steal all of the food stands.
When teachers get in the way of Eren trying to head to the Titans' building to retrieve his chee-burgs, Marco, along with his classmates stand up for him and come between them. After Eren and the others venture into the principal's office, Marco and Ilse follow them, with him holding a camera while Ilse commentates.
- Jean Kirschtein - Marco's positive outlook and polite attitude naturally attracts even the most unapproachable of people, namely Jean. The two have near to nothing in common, but are apparent best friends with a strong level of trust.
- Ilse Langnar - The pair develop a rapport between one another after he returns her journal to her which had been repeatedly snatched away by the likes of various election candidates. Ilse admires Marco's selflessness and endorses him for President, resulting in him winning by a landslide. He then accompanies her to report on the right to retrieve the school's snack stands from the Titans.