Kaito is a high school freshman who enjoys solving puzzles, feeling insulted whenever they are used for hurting others as his parents were killed while attempting to solve a deadly puzzle. He carries the Solver title, 'Einstein'. One day, he discovers the Orpheus bangle which attaches itself to his arm. Under high levels of stress, he enters a strange state that allows him to use his brain to its fullest potential and see the solution for any puzzle.

Kaito does not seem to have many interests other than solving puzzles. As seen in the first episode, he will e.g. use school property (in that case school desks) to solve puzzles, if he can't "see" through them right away. His friend Nonoha scolds him for that and slacking off, not refraining from physical violence as well. Although it is still uncertain, what kind of feelings he might have for her, Kaito cares a lot about Nonoha, not letting her come in harms way. He even hides the fact that one of her friends, the kindergarten teacher Madoka, is in fact a P.O.G. Giver. Kaito is very outspoken about Nonoha's cooking, calling the "Nonoha sweets" "weapons of mass destruction", which causes Nonoha to punish him physically. As for now, Kaito is the only one who openly dislikes Nonoha's cooking.

Source: Wikipedia