Feeling unsettled about the future, high school student Ryouhei Arisu often escapes the reality of life. After hanging out at a bar, Arisu and his best friends, Daikichi Karube and Chouta Segawa, wait for the first train to arrive in the morning. Suddenly, a colorful array of fireworks set off in the sky, and an enormous blinding firework renders them unconscious.

The trio finds themselves back at the bar covered in dust, discovering that the city has become a barren wasteland. But instead of being worried, Arisu feels alive for the very first time in his life and relishes the freedom of this lifeless city. However, his bliss is cut short when the group rashly enters a festival venue. Seeing its delicacies and lively ambiance, they think the place is a dream; unbeknownst to them, it will be the setting for their first deadly game.

Together with his friends, Arisu slowly enters the mysterious area known as the Borderland—an unknown country where every game puts their lives at stake, and a single misstep can lead to their demise.