In the immediate aftermath of the Kaiju No. 8 incident at the Tachikawa base, where Kafka Hibino’s secret identity was revealed to save his comrades, the Third Division finds itself under a cloud of suspicion and internal reorganization. This side-story light novel delves into the untold daily lives and off-duty moments of the division’s members as they navigate the fallout from Kafka’s exposure and the looming threat of a more intelligent enemy.

The story follows the young rookies Reno Ichikawa, Kikoru Shinomiya, and Iharu Furuhashi as they are reassigned to temporary posts across different divisions. While Reno attempts to prove that a cadet with no natural talent can still contribute through strategy and willpower, Kikoru struggles with the weight of her father’s legacy and the secret she keeps for Kafka. Meanwhile, Vice-Captain Soshiro Hoshina sharpens his blade techniques in isolation, haunted by his failure to detect the humanoid kaiju hiding in plain sight. Captain Mina Ashiro faces political pressure from higher command, forced to justify why her division protected a monster. Through flashbacks and quiet character-driven scenes, the narrative explores the rigorous training routines, the camaraderie of the mess hall, and the fear of kaiju infiltration that permeates the organization.

As the division participates in the Sagamihara Neutralization Operation, the narrative cuts between the explosive front-line battles and the logistical nightmares occurring behind the scenes. A central arc follows the bureaucratic struggle to classify Kafka not as a weapon to be dismantled, but as an asset. This culminates in the tense confrontation between Kafka and Director General Isao Shinomiya, viewed through the eyes of the operators monitoring his vital signs, including the young prodigy Konomi Okonogi. The light novel expands on the world’s lore by detailing the scientific analysis of Kafka’s core and the history of previous numbered kaiju weapons, setting the stage for the Kaiju Weapon Arc where Kafka is reintegrated as a sanctioned, yet monitored, operative of the Defense Force.