Gakuen Bakuretsu Tenkousei!

A strong girl transferred to a new girls' school and moved in with a room-mate. That day, she got the school regulation girl upset at her. Next day, her room-mate is missing and she went searching the school for her room-mate. What she finds are a bunch of nasty stuff. If you can get her pass the four bad endings, she can rescue her room-mate, even if a bit late.

[From Li's Fun House]