From the start, he was known as a delinquent. When he was in middle school, he destroyed a biker gang, earning him a town-wide reputation of wildness and toughness. Though people often mistakenly believe him to be a member of a biker gang or a person who enjoys violence, he actually does not have any inclination to be violent. When his denial of enjoying "feminine" hobbies like sewing or knitting was pushed to the extreme, it unexpectedly established his position as a juvenile delinquent. He drapes his school uniform over his shoulders in a punk-ish style to emphasize the style he wishes to embody. He acts out against any authority figure, but speaks politely to the protagonist and his other seniors. However, when he sometimes gets flustered he tends to threaten people, occasionally getting into fights and scraps. Often, his reputation for being tough and mean comes as a result of misunderstandings. For example, he once went after a rowdy biker gang, but only to stop them from disturbing his mother. He always obeys his strict curfew because his mother makes a fuss when he doesn't.

His father is deceased. Before Kanji's father died, he told Kanji, "If you're a man, you have to become strong." Kanji thought his father was telling him he wasn't a real man, which angered him and caused him to become insecure about his masculinity. As a result of this, Kanji drastically changed his appearance and began isolating himself from others. At the beginning of Persona 4, Kanji has no known friends.

Compared to the rest of the team, Kanji tends to be a bit slow on the uptake. However, he is straightforward and decisive. Through the game he realizes that his impulsive actions can drag others down, and that he can balance that by instead giving them his support.