After their town is destroyed by kaiju, childhood friends Kafka Hibino and Mina Ashiro both vow to become members of the Defense Force to fight kaiju together. Mina, now 27, has since become the captain of the Defense Force's Third Division while Kafka, now 32, has failed the examination numerous times and works as a member of a clean-up crew that disposes of kaiju remains after battle. Kafka meets a young part-time worker in his company, Reno Ichikawa, an aspiring Defense Force member, who reignites his desire to become part of the Defense Force. However, a parasitic creature enters Kafka's body through his mouth and he gains the ability to turn into a kaiju. After escaping from the Defense Force, Kafka is given the code name "Kaiju No. 8" and decides to apply while keeping his kaiju form a secret.
