Kaiju No. 8 (怪獣８号, Kaijū 8-gō) is a Japanese anime series based on the Kaiju No. 8 manga by Naoya Matsumoto.

Kafka Hibino, a 32-year-old man, is unsatisfied with his job as a sweeper. From a young age, he has aspired to join the Defense Corps and kill kaiju for a living. After a few failed attempts, however, he gave up on his dreams and resigned himself to the mediocrity that provided a decent paycheck. Nevertheless, when an ambitious, 18-year-old recruit named Leno Ichikawa joins his cleaning team, Kafka is once again reminded of his desire to join the military.

Following a chain of unfortunate events and an interaction with the junior sweeper, Kafka encounters a parasite-type kaiju that forces its way in through his mouth—turning him into a humanoid monster. With his newfound powers, Kafka aims to give his lifelong dream a final try.