In a Kaiju-filled Japan, Kafka Hibino works in monster disposal. After reuniting with his childhood friend Mina Ashiro, a rising star in the anti-Kaiju Defense Force, he decides to pursue his abandoned dream of joining the Force... when he suddenly transforms into the powerful "Kaiju No. 8." With help from his junior colleague Reno Ichikawa, Kafka hides his identity while striving towards his life-long dream of passing the Defense Force exam and standing at Mina's side. But when a mysterious intelligent Kaiju attacks a Defense Force base, Kafka faces a crucial decision in a desperate situation...