After the obliteration of their old neighborhood, cherished, lifelong companions Kafka Hibino and Mina Ashiro make a settlement to become officials in the Guard Power — a mobilized association entrusted with shielding Japan from epic beasts known as "kaijuu." Many years after the fact, the 32-year-old Kafka has in essence abandoned his fantasies of chivalry. All things being equal, he tidies up the remaining parts of the butchered kaijuu after they are crushed by brave warriors — including Mina, who has effectively accomplished their common objective.
After gathering his new colleague, Reno Ichikawa, Kafka faces a reflection of his past self: an aggressive young fellow whose one craving is to battle as an individual from the Safeguard Power. Tragically, the two are before long associated with an oddity experience with a rebel kaijuu. However Kafka exhibits his intrinsic gallant nature and salvages Reno from specific destruction, he is left seriously harmed.
While the two men recuperate in an emergency clinic, Kafka is apparently gone after by another of the monsters. Thus, he acquires the capacity to change into a humanoid kaijuu with the strength and powers of the enormous beasts threatening Japan. Named "Kaijuu No. 8" by the military, Kafka makes plans to involve his recently discovered gifts for everyone's benefit. Integrated by common regard, Kafka and Reno set off to join fighters like Mina at the front of the Safeguard Power.