The internet is home to countless urban legends, but the most prominent is the mysterious gamer known only as "Blank." Behind breaking records in hundreds of games, Blank is just two shut-in NEET siblings: the manipulative 18-year-old Sora and the 11-year-old detached genius, Shiro. Together, they are an unbeatable duo with zero losses to their name.

One day, the siblings receive an anonymous email challenging them to a chess game. Upon securing a flawless win, they are immediately summoned into a colorful alternate world. A playful boy named Tet, who introduces himself as the "One True God," tells them that the world of Disboard has a unique system for resolving disputes—any and all disagreements are resolved through simple games. Furthermore, of the 16 races inhabiting the realm, humanity is ranked the lowest and least powerful, barely scraping by with a kingdom consisting of a single city.

In a world that has yet to see war or bloodshed in centuries, Sora and Shiro quickly make a name for themselves as they set their eyes on an ambitious goal: to defeat Tet with their gaming wits and conquer this new world.