エンジェル・ハーツ

In a certain girls' high school, students have begun to mysteriously disappear. Authorities suggest that a secret society is at work. A spy needs to be sent in order to solve the mystery, and this mission falls into the hands of this game's hero. His boss explains to him that the quest is dangerous, indeed: many students associated with the mysterious cult have gone rampant and will attack any trespasser on sight!.

[From MobyGames]