Kato’s parents actually died before he did.
He has quite a sweet, caring side, taking care of his brother, Ayumu, and a sense of justice stronger than anyone else — wrongness and wrong doing can simply not be forgiven by him.
Despite his imposing stature and strength, he’s actually not all that confident in himself, and there is actually a scene that has him shaking in his boots before a big challenge.
However, he has the real “courage” to overcome such fear, and go face hardships and difficulties.
He used to always hang out and go along with Kurono back in elementary school.
Idealizing Kurono’s fearlessness still has a strong impact on the way that Kato lives his life now.
---- Oku-sensei’s comment:
If Kurono is the ordinary high school student, then Kato is reflects sort of the ideal high school student, in my mind.
I think I might have been influenced by John McClane from the Die Hard series.
For example, Kato might feel regret in that he has to fight against his will, and might think, “Why does it always gotta be me involved in this?” but he’ll actually wind up succeeding.
I had the idea of how and where I’d have Kato killed in the story from the beginning.
I was also originally planning that, “Everyone but Kurono dies somewhere in the story.”