I feel the same as you.
At first, I thought Jooin was the one having a hard time but then I realized that Cain is the one. Cause his pain is silent. Like he does not want to show it. Maybe what the author is trying to tell us is that all that Cain needs is to be loved.
I'm starting to feel like Jooin is NOT a good match for him. The dude can't even pick up that he is not doing well. All he is worried about is: "some sappy love story with Yahwi. Frankly they should just get together and let Cain be."
Unfortunately, that's the narrative BL stories have been feeding us with, the abused always goes back to the abuser based on some BS background "we knew each other since childhood" story.
Personally, Jooin and Yahwi (the two toxic dudes) can end up together, and I don't care at this point because that's the path the author is leading us to.
All I wish is that they respect Cain's side of the story and not turn him into some kind of evil human.

Man... I just want Cain to just have his own love life and not get tangled by these two