Shoujo Shikkaku

A mysterious transfer student arrives to the third year, class C for Hanazono Girl's Middle School.
Akane is a plain and simple girl who was tired of her overbearing friends, and silently thinks that it would be okay if the world were destroyed. One day, all the girls of the class awake to find themselves in a deserted school, with mysterious timers counting down. Each girl is shackled to another girl, and these pairs must work together to survive a 7-day Battle Royale. As it turns out, Akane is paired with the mysterious transfer student.

Friendships crumble, hopes are lost, and sanity is tested as the game starts off with a bang!