Ganta is the only survivor after a mysterious man in red slaughters a classroom full of teenagers. He's framed for the carnage, sentenced to die, and locked away in the most twisted prison ever built: Deadman Wonderland. And then it gets worse.

Fear, survival, instinct. Thrown into a foreign land with nothing but hazy memories and the knowledge of their name, they can feel only these three emotions resonating deep within their souls. A group of strangers is given no other choice than to accept the only paying job in this game-like world—the role of a soldier in the Reserve Army—and eliminate anything that threatens the peace in their new world, Grimgar.

When all of the stronger candidates join together, those left behind must create a party together to survive: Manato, a charismatic leader and priest; Haruhiro, a nervous thief; Yume, a cheerful hunter; Shihoru, a shy mage; Mogzo, a kind warrior; and Ranta, a rowdy dark knight. Despite its resemblance to one, this is no game—there are no redos or respawns; it is kill or be killed.

It is now up to this ragtag group of unlikely fighters to survive together in a world where life and death are separated only by a fine line.

Sakamoto, an unemployed young man, is one of the world's top players of an online fighting game called Btooom! One day, he wakes up on what appears to be a tropical island, although he doesn't remember how or why he got there.