A 32-year-old former kaiju cleanup worker. After swallowing a mysterious small kaiju, he gains the ability to transform into "Kaiju No. 8." He decides to try again to fulfill a childhood promise to Mina, the captain of the Third Division, and joins the unit. While his combat suit's unleashed power is low, he uses his extensive knowledge from the cleanup industry as a weapon. During the attack on the Tachikawa Base by Kaiju No. 10, he transformed into Kaiju No. 8 in front of his comrades and was subsequently taken into custody by the Defense Force.

A super-elite talent hailed as the greatest prodigy in history, having skipped grades to graduate from a foreign anti-kaiju university. She is the daughter of Isao Shinomiya, Director General of the Defense Force. Wielding a specialized axe-type weapon, her extraordinary combat sense gave her the strength of a platoon leader even before her official enlistment.

A member of the Defense Force's Third Division and Kafka's former junior from the cleanup company. Initially, he looked at Kafka with cold indifference for giving up on his dreams, but he came to respect him after seeing his character. He was present when Kafka first transformed into Kaiju No. 8 and has been supporting him to keep his identity a secret. He excels in combat using freezing rounds.

A member of the Defense Force's Third Division. He is the scion of Izumo Tech, the nation's largest manufacturer of anti-kaiju weaponry. An elite who excels in both academics and athletics, he graduated at the top of his class from the Tokyo Anti-Kaiju University.

A member of the Defense Force's Third Division. Formerly a rising star in the Ground Self-Defense Force, he requested a transfer to the Defense Force. Though he is taciturn and hard to read, he is always calm and places great importance on teamwork.

A member of the Defense Force's Third Division. A talented fighter who graduated at the top of his class from the Hachioji Anti-Kaiju Technical College. While he is competitive and often blunt or rude, he is a compassionate mood-maker for the team. He feels a strong sense of rivalry toward Leno, but also considers him a true brother-in-arms.

The lead operator for the Defense Force's Third Division. She has a serious, inquisitive, and scholarly nature, and also serves as an assistant to Vice-Captain Hoshina.

The Vice-Captain of the Defense Force's Third Division. He comes from a lineage of kaiju slayers dating back to the Muromachi period. A specialist in swordsmanship, his skill in neutralizing small to medium-sized kaiju surpasses even that of Captain Mina Ashiro.

The Captain of the Defense Force's Third Division and Kafka's childhood friend. Having neutralized hundreds of kaiju by the age of 27, she is one of the most popular and powerful captains in the force. She is an expert with long-range heavy weaponry and specializes in taking down giant kaiju.

The Captain of the Defense Force's First Division. While his personal life is messy and his character is full of flaws, he possesses a natural genius for combat, making him "Japan's strongest anti-kaiju asset." He demands nothing but results and raw strength from his subordinates.