Twenty-six-year-old Ryouhei Arisu now has a fairly decent life working as a guidance counselor at school and being married to Yuzuha Usagi, a mountaineer he met eight years ago. When he discovers that his wife is due to give birth soon, he quickly rushes back to Tokyo to accommodate her.

However, just as all seems well for Arisu, his current location is suddenly tormented by a heavy rainstorm. While urgently trying to travel through the oppressive weather, he is crushed by a falling billboard. This near-death experience transports Arisu back to Borderland—an unknown country where one must play grueling, sometimes sadistic games to determine whether they live or die.

Recognizing the grave danger he is in, Arisu perseveres to return to the real world in hopes of reuniting with his family once again. But as he slowly understands the game, he realizes that returning may not be as simple as it seems.