Kamisama no Iutoori

Summary

Takahata Shun's day at high school begins just as normal and boring as ever, but it doesn't end that way. After his teacher's head explodes, he and his classmates find themselves forced to play children's games, such as Daruma ga Koronda (a game like Red Light/Green Light), with deadly stakes. With no idea who is behind this mysterious deadly game session, and no way of knowing when it will finally end, the only thing Shun and other students can do is keep trying to win... (Source: MangaHelpers)