It's a trap

This new character seems like a boy to me.

I don't know why, but I think that he's cross dressing and offering "services" to gain money for his sick father.
Maybe the psycho kidnapped him only because he was in a shady alley, wich is why Sangwoo 2.0 acted directly.
Also, he has a very flat chest (Of course, girls can also be flat chested).
Also, how could he easily undress a boy, if he wasn't one himself , he seems very shy and sensitive...

But it's just a theory
A yaoi theory