Ryouhei Arisu is a high school student without any ambition and feels his life is meaningless until a fortuitous evening changes everything. Along with his friends Daikichi Karube and Chouta Segawa, they witness a massive firework explosion that teleports them to a mysterious place called the Borderland. In this new world, they become involved in a treacherous game where survival hinges on completing risky tasks. Despite the danger surrounding them, Ryouhei finds an exhilarating sense of purpose unlike any he has ever experienced before. Together, they must navigate their way back home while being challenged at every turn.