Modern-day middle school girl Hideyoshi is mysteriously hurled into a world resembling the warring states period of Japanese history, only this time it's inhabited only by women. This world's Oda Nobunaga is gathering the legendary Crimson Armor so she can rule the world, and for some reason needs Hideyoshi's help to do it.
Spike Spiegel, a bounty Hunter with a dark past, lives on bounty to bounty, barely making it each time, or not making it at all. His partners Jet Black, Faye Valentine, Ed and Ein the dog all help him in his adventures from planet to planet.
After death, humans go to either heaven or hell. But for some, at the instant of their death, they arrive at the Quindecim, a bar attended by the mysterious white-haired Decim. He challenges them to the Death Game, wherein they wager their lives and reveal their true natures. Decim himself is the ultimate arbitrator of who wins and who loses, who lives and who dies.
After death, humans go to either the eternal void or are reincarnated. However, where there's doubt as to were to place some occasional souls, these instead arrive at bar Quindecim, with no memories of having died. Decim, the bartender, challenges them to the Death Game, wherein they wager their "lives" and reveal their true natures. Decim himself is actually an arbiter in charge of deciding the fate of those that arrive at Quindecim - by pulling the darkness from deepest within them, he judges their ultimate fate.
Genius gamer siblings (plus being NEET & hikikomori) Sora and Shiro are known as the undefeatable “__” (blank). Their talents and skills are so good they are considered as urban legend. One day, a young boy named Teto appears before them, claiming to be the “God” of another dimension where Sora and Shiro are summoned to, in which no violence is allowed and everything is decided by a game. Of the 16 different races residing in this world, “Humanity” is the weakest. After having the vast majority of their lands captured by the other races and being driven to the brink of extinction, Sora and Shiro challenge these one-of-a-kind battles of the intellectual powers in order to save Humanity.