Fuyu

Fuyuhiko is initially incredibly stand-offish and rude to the other students on the island. He claims he's not going to play at being friends with anyone, and when he is questioned about this in Chapter 1, he states clearly that he would not hesitate to kill anyone of the others. He makes frequent references to his yakuza background and seems adamant at presenting this sort of "lone wolf" attitude. Fuyuhiko doesn't simply want to make friends but considers it not worth his time and beneath him. Despite this, as early as chapter 1, he shows signs of this perhaps not being all true, with him "happening to walk by" the lodge where the other students were having a party, despite claiming that he had no interest in going.

When Fuyuhiko does interact with the others (by choice or otherwise), his attitude is combative and irritable. He's easily angered, often threatening and/or insulting other people when they disagree with or complain about his actions. He frequently uses the word boke (a particularly pejorative way of calling someone an idiot, often translated as all sorts of profanity), and will punctuate his statements in an argument with it. He avoids any proper relationships and he's used to being treated with caution by everyone; even to the point of threatening to murder someone, especially Mikan Tsumiki, and he acts similarly around her to how Hiyoko Saionji does. In particular he despises Mahiru Koizumi because of her stern attitude and refusal to back down to his threats.

After deciding to change in Chapter 3, because of Peko's sacrifice and him realizing his own mistakes, Fuyuhiko became more sociable and avoided bad-mouthing people to the best of his abilities. He even seems to become one of the group's most loyal and steadfast members, though still short-tempered and impulsive. He tries to help others and is shown to openly care about them, even Nagito Komaeda when he was about to die from Despair Disease. Peko's sacrifice is obviously a sensitive subject for him. He takes over Mahiru's role as the tough but fair member of the group always being on everyone's especially Kazuichi Soda's case but also being very helpful and willing to deal with anyone's problems. He's also very level headed in spite of his bad temper and is very intelligent.