I think Yeongwoon left/ghosted him because of that chapter where it showed that Yw saw Seo-In was kissing someone and I think one of them is the person Yw likes and he disappeared bc it hurt him....
this is just my theory though
The one he saw kissing was his brother even when he sees him with the actor he used to manage he said he resembled his brother I don't know how the brother passed but yeongwoon says was his fault (feels guilty)
BTW the 1st chapter we see yeongwoon walking all bloody and barefoot what we are seeing are flashbacks before it all
YEONGWOON WHAT ARE YOU DOING??!?!? WHY WOULD YOU SAY THAT..... YOU'LL REGRET THAT SO MUCJ OMFG... I CAN'T ANYMORE......