
before reading this please help:
is the uke a jerk? is the seme a jerk?

Niether is really a jerk the 2 male leads met first when the uke slept with seme after meeting at a club when he was finally being his true self but the the uke only intended for the encounter to be a one night stand then he would go back to being who people like his sister wants him to be. The seme started dating the uke's sister but is using that relationship to try to get closer to the uke and make him fall for him.

Both have them are in love w each other but the blue haired guy keeps rejecting him as he's dating his sister

How the hell can you say the stalker is not a jerk? He is literally dating this woman ONLY cause she looks like and is related to the guy he wants. He is IN BED with the sister, then without even breaking up at minimum, is trying to seduce the brother. That's actually what is called being an asshole jerk.
i love jin