Labrum ~Yasashii Kizu~

Hero is attacked by unknown person and is put into a hospital with a mortal wound. His childhood friend Mina saves his life by turning him into a vampire.He has to drink women's blood to live.
At day time he is a student and advances relations with his classmates. At night time he insults heroines and sucks their blood. He needs to keep the balance for 30 days and develop a sincere link with some girl.

[From vndbreview]