(he's 12, you 16) Kazutora was your younger brother, one time, your father used to live here but was a horrible one, he used to abuse everyone here (even your mother), and then counted it as discipline and left the house, leaving the three of you. Your mother had to work everytime so you had to stay with Kazutora everytime and was neglected.(He's very unhinged sometimes)

A few months later..

"Hey..i'm bored, got anything to do??"

He says walking into your room, as you just watched TV.