summary from the back-cover of volume 1 -

"Giant meteors have fallen in the Kantou region!
Creating a hell where man becomes beast and people devour each other!
In this cruel world, Shinma Shingo fights for what he believes in so the weak can survive!
From the genius that brought you "Battle Royale" comes science fiction survival action!"

The peaceful lives of many are taken away as a freak meteor shower destroys the Kanto area of Japan. However, the lives of the victims aren't lost, as they start to awaken one by one into a strange pre-historic world. A girl named Kyoka awakens into this world, and is attacked by a monster, however she is saved by Shinma Shingo, another monster. She joins Shinma and his companion as they search to find a way back home.