Kokichi describes himself as an evil supreme leader, and often claims that this title is the reason behind many of his questionable actions as if he is expected to fulfill his role. He is an elusive and manipulative person who unabashedly tells lies and says whatever he's thinking. He is also strangely straightforward about his supposed evil nature, openly claiming to be a leader of a large secret society, admitting to being a liar, and saying he has done nothing but bad things. Among other things, his organization supposedly has covert agents in every country, control over all the mafias in the world, torture as a form of punishment, and Kokichi's defeated opponents apparently will get sent to Siberia. However, none of his claims have been confirmed, and the other students think he's either lying or delusional.

Fitting his appearance, Kokichi often acts notably child-like, with at least some of it appearing genuine while part of it also could be just his attempt to use his looks to his advantage. He is sometimes shown to have child-like excitement and innocence, as he gets very excited about "cool" new things like the Exisals and the morphing Trial Grounds. He often acts playful and seemingly appears more ignorant than malicious during the first time he meets K1-B0. He is also notably interested in games and often has a strong desire to be a winner and play them seriously while also having fun along with them, with one of his principles being "to have fun" with everything he does.