A 32-year-old man working as a Kaiju disposal professional while pursuing his dream of joining the Defense Force. After swallowing a mysterious small monster, he gains the ability to transform into the humanoid Daikaiju 'Kaiju No. 8'. Combat power released: 1% (Human form) / Fortitude 9.8 (Kaiju form).

Kafka's childhood friend and the Captain of the Defense Force's Third Division. A top-tier officer who uses a massive specialized cannon as her primary weapon, capable of obliterating giant Kaiju in a single shot. Combat power released: 96%.

Kafka's reliable junior and first partner. He was the first to learn Kafka's secret as Kaiju No. 8 and protects him. He shows incredible growth, eventually wielding Numbers 6. Combat power released: 51%.

The daughter of the Defense Force Director General and a certified genius rookie. One of the comrades who shares Kafka's secret, she fights on the front lines using a massive battle axe and the Numbers 4 suit. Combat power released: 84%.

Vice-Captain of the Defense Force's Third Division. Usually appears cheerful with his eyes closed, but possesses sharp insight—having recognized Kafka's potential and recruited him despite a low release rate—and exceptional dual-wielding swordsmanship. Combat power released: 92%.

Captain of the Defense Force's First Division and the strongest active-duty officer. In his private life, he is a shut-in obsessed with gaming and online shopping, but in battle, he displays overwhelming power using retinal implants from Kaiju No. 1 to perfectly predict enemy movements. Combat power released: 98%.

A fellow recruit who joined the Third Division with Kafka. He feels a rivalry toward Leno Ichikawa and possesses the qualities of a 'Flash Adapter,' whose suit synchronization rate explodes momentarily during heightened emotions or crises. Combat power released: 40–50%.

The heir to 'Izumo Tech,' a major corporation that develops specialized equipment for the Defense Force. An elite officer with strong pride and a sense of responsibility, determined to prove himself in the Defense Force through his own skill rather than his family's influence. Combat power released: 30%.

The Director General of the Defense Force and Kikoru's strict father. A living legend who led the Defense Force while masterfully wielding armaments made from the remains of Kaiju No. 2.

An intelligent Daikaiju capable of human speech and mimicking human form. The root of all evil, it constantly evolves by absorbing the memories and techniques of defeated Defense Force members and manipulates numerous lower-class Kaiju to drive humanity toward destruction.