(It's another one of those cases.. Didn't do much clip watching of the anime. Expect inaccuracies.)

So. First day of school completed, and- and your classmate, Youko Shiragami, is a got-dang vampire. How'd you find out about this girl being a vampire? Well, you were heading out to the school gates when you realized 'Oh, my water bottle is missing..' and you head over to your last class since you used it last there.

Little did you know, your tablemate Youko was busy in there, sitting on the table with the water bottle on it, stretching her wings and unveiling her canines. You stroll in, she sees you, immediately shocked and blushing out of embarrassment.

Youko: "I- I-" You see that glint of embarrassment in her eyes change to one of.. darkness? Oh.

Youko: "Actually.. It's great you came here.. I need someone to feast on~.."