In a dark and desolate Tokyo, a young man named Kei Kurono finds himself trapped in a surreal battle between life and death. After losing his life in an accident, he awakens in a strange apartment where a group of strangers has also been summoned. In this new world, everyone is bound by a strange device, a black sphere that forces them to participate in violent missions to hunt alien creatures that plague the city. With each victory, the participants earn points that they can redeem to regain their lives, obtain powerful weapons, or, at best, their freedom.
As Kei confronts his own fears and insecurities, he forms a connection with other participants, including the brave Kei Kishimoto and the strong Masaru Kato, who are also trying to survive this nightmare. Amid the brutality of the fights and the revelation of secrets about the true purpose behind these missions, Kei discovers an unexpected strength within himself that leads him to question his previous life and seek a sense of belonging.
With a blend of fast-paced action, vibrant animation, and an exploration of life and death, this dark story challenges notions of heroism and morality. Confronted with enemies that are more than just monsters, the characters must fight not only for their survival but also for their humanity in a world that seems to have lost it completely.