i'm packed off to a boarding school in the middle of nowhere...oh and i don't think they're humans~1

Christine. That's her name. The girl who arrives in the boarding school, completely unaware that it was a boy school. She gets to know six friendly roommates, one who is plagued with memories of his gruesome childhood.

There was one whom she hated, but after a few fights, they made up and things between them became heated. Little did any one of them noticed there was a vengeful killer in their school until the first person to die was a teacher everyone hated.

Can they return to school in time to find out who was the culprit, or would the students in the school of Dark Night suffer because of a fateful incident which did not involve the innocent?