Ulrich is the introvert of the group, rarely expressing his feelings and acting evasive whenever someone asks him about himself or his family. He seems to have trouble opening up to people and hides his feelings in order to use them all the more explosively in action.

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One of Ulrich's key characteristics is his affection for Yumi, a fact that has caused countless instances of tension and drama between the two of them due to the fact that he has never admitted it. Even his friends have occasionally admitted to finding his hesitation tedious, and the constant excuses Ulrich makes to himself are only underlined by his jealousy whenever Yumi spends is approached (or is seen approaching) anybody else. In rare instances, his feelings for Yumi can cloud his better judgement by making him pull reckless stunts in her favor. One time was in Marabounta when he humiliated himself by falling off the diving board in an effort to spy on her when she was with William. A more notable time was in The Chips are Down when he became so worried about Yumi moving away that it resulted in his temporary expulsion from the team when he went behind his friends’ backs to launch a Return to the Past (which strengthens XANA) to cheat at the lottery and donate the winning ticket to Yumi’s parents.

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Ulrich behaves childishly whenever he is beaten or humiliated in her presence, refusing to congratulate Yumi after she tied him in a fight in X.A.N.A. Awakens and getting mad from embarrassment after William helped him out of the pool in Marabounta. This implies he has a massive inferiority complex which, combined with his ability to constantly make excuses for himself, often prevents him from maturing or gaining self-confidence. He also is known to take it out on others, including one time he played a rather cruel joke on Johnny, a younger classmate, just because he admitted to Ulrich that he liked Yumi (in The Pretender). This inferiority complex is also enhanced by Ulrich's extremely strict and condescending parents, particularly his father, who Ulrich has had the least stable relationship with anybody else due to his inept laziness when it comes to his schoolwork.

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However, in times of crisis Ulrich is able to drop these feelings of inadequacy for the sake of his friends. He is brave and extremely competent on the battlefield (both on Lyoko and Earth), and is also shown to be unwilling to let anyone, even his rivals or bullies, get hurt by any of X.A.N.A.'s attacks. Ulrich becomes incredibly worried whenever his friends are hurt, and it is during these times that his feelings tend to surface. The first example of this is in the episode Killer Music, when Odd is sent to the hospital in an emergency condition and slips into a coma. Ulrich blames himself for not being there when Odd had needed him and insists on riding with him during the ambulance ride despite protests from the principal. A similar situation occurs in the episode Cold War, when Yumi is trapped under a fallen tree during a deadly blizzard. After several failed attempts to free her, he cries as he tells her that he needs her while holding her and screams in grief when she appears to have died.

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In Vertigo, it is revealed that Ulrich has vertigo, which is a chemical disorder that causes dizziness in the presence of high altitudes. He shows signs of it when attempting to climb a rock wall in the gym, which reveals the condition to his friends. This condition doesn't seem to affect Ulrich much before this point, except for in the prequel, when he hesitates to slide down the ropes to the factory floor. Having vertigo does not seem to be a hindrance on Ulrich when on Lyoko, with the notable exception of the episode Bad Connection.

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In Echoes Ulrich admits to Odd that he likes being a hero, implying that he sees his time on Lyoko as a way to prove himself.