it’s definitely because of the blood, sunbae came home traumatised and decided as a way to rid of those thoughts he was going to sleep with the MC, who he knew loved him and he loved back. Sucks that it had to end that way but ig miscommunication really is the root of all evil
i get what your saying but i want to add to your point. i think deeper than that. yes the throwing up emotionally affected the mc but he was already struggling and dealing with the aftermath prior to the puking. it was just the cherry on top. he treats you like a toy, doesnt care about how rough he is only to make you bleed and then pukes....
reason for puking doesnt really matter
but it goes deeper like i said. dont think its just because he saw blood.
the reason he bled is because of the lack of concern about the mc.
no prep nothing. just raw dog fucking roughly for the first time. he didnt care about the Mc the Mc safety or his enjoyment. just like i said, a toy.
and when he saw blood it hit him. its much deeper than just blood. its the blood and the quick fall from his high. he got nauseous because of the rush.
Maybe the sunbae threw up because of the blood or the thought that he hurt the MC. I don't think he threw up because of sex. Either way, the MC misunderstood and the sunbae didn't explain. They could've been a cute couple, but it's too late for them now. Lol