Despite his serious attitude, he is actually caring towards others, and doesn't usually like showing his true feelings. Michael and many of the other members of the party are able to see him for how he truly is despite his Military upbringing. When he sarcastically refers to himself as an oaf, Jesse tells him that he is a "gentle oaf". There are also various parts of the series when Michael or another party member talks about Markus' personality, in which he gets embarrassed and tries to end the topic quickly.
He is also one to get mad easily and can get out of control whenever things get out of hand, in which he's usually yelling at someone, and someone else usually has to calm him down. Markus is also someone who does not simply take things at face value. Despite what people tell him what he should believe or what paths he should follow, he is not easily swayed. He is also a very tolerant person because despite the fact that people, such as Q.Q. and Lelouch betray and abandon him during the Series, he still tells them and other people that he still considers them to be his friends.
Compared to Jesse, whom dresses far more regally and fancy, Markus prefers simplicity with wearing only a unique uniform built from an unknown material. Eins wears boots for all terrain travel and military-like pants, he has shoulder length hair which he keeps out of his eyes, Markus usually carries a Heavy Sword with him.