Everything started at the beginning of the previous school year; it's been barely one year.
Don't forget this: having Kate on her knees also means he'll be the overlord and supreme ruler of all the other bitches. This game is a Bildungsroman, a story of growth and self-improvement for our soon-to-be gigachad MC.
I'd say a harem of obedient bitches is a nice reward for one year of suffering. Has anyone here been bullied at school to then be rewarded with a harem of smoking hot bitches? Please, raise your hands!!