Affiliation: Vice-Captain of the Third Division, Japan Anti-Kaiju Defense Force. Traits: Born into the Hoshina family, a lineage of Kaiju slayers dating back to the Muromachi period. A specialist in close-quarters combat using blades, his skill in neutralizing small to medium-sized Kaiju surpasses even that of Captain Mina Ashiro. While he usually acts like a playful cynic speaking with a regional drawl, he is deadly serious and makes cold, calculated judgments in battle.

Affiliation: Captain of the Third Division, Japan Anti-Kaiju Defense Force. Age: 27 (at the start of the story). Traits: Childhood friend of the protagonist, Kafka Hibino; they promised to join the Defense Force together. With a record of slaying hundreds of Kaiju, she is one of the most powerful and popular Captains in the force. She excels at neutralizing giant Kaiju and is an expert with heavy firearms and sniper weaponry. Usually cool and stoic, she rarely shows emotion but possesses a kind heart that cares for her troops and Kafka.

Affiliation: Third Division, Japan Anti-Kaiju Defense Force (later attached to the First Division Captain). Age: 16. Traits: A genius girl who became the youngest Defense Force member in history. As the daughter of Isao Shinomiya, Director General of the Defense Force, she has received elite training since childhood. Possessing high combat ability and pride inherited from her father, she initially treated Kafka coldly but gradually came to trust him after recognizing his character and strength. An expert in close combat who wields a specialized "Identified Kaiju Weapon."

Captain of the First Division, Japan Anti-Kaiju Defense Force. Traits: Acclaimed as Japan's strongest anti-Kaiju combatant. He is Kikoru Shinomiya's direct superior. He wears the "Numbers 1" suit, a special piece of Identified Kaiju Weaponry, and draws out its maximum potential in battle. He possesses a unique combat technique akin to precognition called "the power to see the future," allowing him to predict and counter enemy movements. While usually a lazy, cynical individual who moves at his own pace, he has a strong sense of responsibility as a Captain and a passionate side that won't hesitate to risk his life for his comrades and subordinates.

Operator for the Third Division, Japan Anti-Kaiju Defense Force. Often affectionately called "Okorogi-chan" by close members and fans.

Age: 32. Dream: To join the Japan Anti-Kaiju Defense Force alongside his childhood friend Mina Ashiro and fight Kaiju. Though he once gave up on his dream, meeting his junior Reno Ichikawa inspired him to pursue it again. Special Condition: After being parasitized by a mysterious small Kaiju, he gained the ability to transform into "Kaiju No. 8." Within the Defense Force, his true identity is a top-secret matter.