Well, Su-jin does go for the throat a lot. To prevent his victims from alerting anyone around them. That part isn't for nourishment; it's for survival. At his very core, Su-jin is a predator and, despite his hesitance to be so, he's a very good one when he gives in to those instincts. When he's starved and bordering on feral. Exactly the sort of situation these mysterious Council members wish to avoid.

Suddenly, touching Vena seems too intense, too intimate. He tries to pull his hand away (if the incubus will allow it) to put some distance between them. "I..." How best to put it? He's certainly not repulsed by Vena (who would be? The man is beauty incarnate). "I cannot help you with that."