In a world plagued by creatures known as Kaiju, Kafka Hibino aspired to enlist in The Defense Force. He makes a promise to enlist with his childhood friend, Mina Ashiro. Soon, life takes them in separate ways. While employed cleaning up after Kaiju battles, Kafka meets Reno Ichikawa. Reno's determination to join The Defense Force reawakens Kafka's promise to join Mina and protect humanity.
Kafka Hibino finally gets another chance to pursue his childhood dream of joining the Defense Force, only to gain the ability to transform into a kaiju himself. While hiding his extraordinary secret, he fights alongside a new generation of officers against increasingly intelligent and powerful threats, forcing him and his comrades to grow stronger as the battle for humanity’s survival escalates.
While the rookie members demonstrate the results of their training and manage to suppress the pterosaur monsters, the attack of the giant "Kaiju No. 10" intensifies even more! Hoshina continues to attack steadily in response to changes in the enemy, but finally reaches its limit. At that moment, what came to Hoshina's mind were Mina's words, who recognized her swordsmanship and entrusted her with her back.