All the creepy vampire men play the cello, because of its full bodied and soothing sound. Though I am amazing he can play it when he banadages up his freak hand.

Since Saya is a vampire, we know that if you've seen the movie, plus there are tons of hints in the first eps, no weight gain from food, goes to the hospital for blood transfusions, etc. But with the flashbacks intersperced in the first eps, it got the impression the creepy cello guy was actually the person that turned her. He fed her his own blood through that kiss. Apparently that does something, because the cut on her face healed.