Is this back story really necessary? I feel like Cain won't leave and that's that.

Cain is one of the main characters, what are you on?? Ofc the main lead will have lots of screen time

i accidentally liked i meant to dislike

Ok but what's the point of the back story? For jooin to cry more?

to show the relationship of jooin and cain in their past life. no one told jooin to cry

Are you slow

Yes