Ryouta Sakamoto is unemployed and lives with his mother; his only true accomplishment is that he is Japan's best player of the popular online video game Btooom! His calm existence is about to change when he finds himself trapped on an island in the middle of nowhere, clutching a little green crystal in his left hand and having no memory of how he got there. To his surprise, someone has decided to replicate the game he enjoys in real life, with the stakes being life or death. The players are charged with murdering seven of their fellow participants and stealing their green crystals in order to return home, armed with a bag full of unique explosives known as "BIM."