Ryouhei Arisu has settled into an ordinary life as a school counselor, married to the mountaineer Yuzuha Usagi and expecting their first child, when a falling billboard crushes him on a Tokyo street. He wakes up back in Borderland, the deadly game-world he escaped years earlier, and is dropped straight into a lethal round called Nine of Hearts with six strangers. Racing to survive and get home before Usagi gives birth, Arisu finds that escaping Borderland a second time won't be as simple as the first.