Btooom!

Ryouta Sakamoto has little to be proud of offline, but inside the explosive combat game Btooom! he is one of Japan's best players. He suddenly wakes on an unknown island carrying a bag of the game's specialized bombs and a green crystal embedded in his hand, then learns that someone has recreated the online competition as a real battle to the death.

The stated way home is to kill seven other participants and take their crystals. Ryouta initially refuses to accept the rules, but other players are far less reluctant to use violence. Drawing on skills that once existed only behind a screen, he teams up with fellow player Himiko and searches for another way off the island, slowly uncovering who arranged the game and why so many unwilling people were chosen for it.