By some of the lines seems like he used to prostitute himself, his brother did box for a little while but stopped soon, which might mean that something happened to him (at the very least it makes it less likely for their parents to be strict since strict parents often have you see through the things you pick up whether you like it or not to teach you responsibility) or either way cuts the possibility of the brother being an over-achiever he'd get constantly compared to, and he looks very used to fighting, both with fists and in a more lateral sense, other than not being above to using underhanded methods to get what he wants. More than a rich brat with an inferioroty complex he sounds like someone that grew up in a somewhat unstable and difficult home situation imo, if he was the former it'd be easier for him to arrange a way to get away from home without having to resort to what he did (which we can convene is a rather desperate way to secure a living place)
ugh that sounds thoughtful and level-headed but damn Kei was still a jerk
Never said he's not a patented a*hole : V
Sure, there's a good chance that he's got reasons to be so twisted, but even if it was it wouldn't excuse. At most, it would help to explain his way of thinking but that's it. °3°
Read the new chapter and you'll understand how Kei grew up....
let me guess, kei is the son of a single dad who works too much/is rich/famous/strict and kei got tired of life at home and having to meet expectations + gets compared to his brother a lot so he left to live by himself. aka every single angsty emotionless seme on the face of the yaoi planet