Technically, since Kim Dan left it's been a hot minute (not just for us, but in the narration too). At first Jaekyung realizes his absence bothers him, then he looks for Kim Dan and when he finds him he's become an alcoholic suicidal sleepwalker. This takes him back to his horrible childhood, he also realizes that he's been hurting Dan, that's why he starts to treat him nicely. I may agree that the sex is a bit soon, they could've gone without it, but at the same time it feels like Jaekyung's character development is validated. Also, in real life you can absolutely reject someone, but what can you expect from a manhwa that revolves around this relationship?
Let's set that aside... Addressing this to you. Coz I think only a boomer can make such topic (not in disrespectful way oc). I don’t know why people come here to give life lessons to others. It’s a comment section dedicated to mangas (fiction), idk... It's a waste of time really. Don't mix what people read and what they do with their life

three instances of him being kind is what makes yall like him? after all he did? yall i pray you guys never get into relationships. relationships are hard work and you have to sometimes put your feelings aside to understand your partner, but with that being said, that does not mean you have to forgive everything they fucking do. And it gets to a point where forgiveness isnt an option anymore.