Fortune Arterial: Akai yakusoku

Kohei Hasekura has lived a live of transferring schools, and now finds himself at Shuchikan Academy. It's a fairly nice Catholic school, but Kohei doesn't care about getting closer to Christ or punishment or anything like that; he's there because all of the academy's students live in dorms. At his new learning place, he makes friends with those around him fairly quickly, and the days go by fairly normally. However, Erika, one of the girls he befriends has a massive secret... She's a vampire.