In a world plagued by monstrous kaijuu, the Defense Corps battles daily to protect Japan. Kafka Hibino, a dissatisfied 32-year-old sweeper for the Kaijuu Cleaner Corporation, harbors a long-lost ambition to join the elite military unit. His dreams resurface when young recruit Leno Ichikawa joins his team. After a life-changing encounter with a parasite kaijuu, Kafka transforms into a humanoid monster, determined to fulfill his lifelong aspiration of becoming a defender against the relentless kaijuu threat.