Probably what happened is he had sex with him but since neither has experience they messed up, he made him bleed, and Hyunwoo panicked and applied some cream and tried cleaning him up. Then the next day he tries to act like nothing happened. But he slipped up in ch14. Look at his face drop when he realizes what he said. Subin then points out it's not cream you would apply to your mouth.
Literally in bed naked with him: http://www.mangago.zone/read-manga/hate_mate/uu/hate_mate-chapter-3/33/
And this is probably an actual flashback:
http://www.mangago.zone/read-manga/hate_mate/uu/hate_mate-chapter-13/52/
The cream, his mention of bleeding
There's too much evidence.
ahhhh I see--- Thank you for reference anon (づ￣ ³￣)づ, and that makes sense
NP. :3 tho I suppose there's a chance the author could still throw a curveball.
why would he have the cream if he wasn't the one who woke up with cum in his ass? Or did he just think it was but it was just the cream