Responses
It was kinda mentioned before that he started going to Hajoon's club to cover for Jitae (so Jitae doesn't have to go) so I guess it has something to do with that.
Also as Jian mentioned he considers himself a villain (for everything that Jitae went through), so he uses it as a self punishment..
It's a form of self destructive behaviour
He's in pain, but he doesn't think he's worthy enough to be hurt. Just like when a teenager cuts their skin when they're overwhelmed.
At least that's what I think
I knew jian didn’t like sex as much as he projected! But what got him into it? He can’t have it without drugs so why does he do it? I understand that he’s using it as an escape but why? What happened to him?