Kenji Endo is the central protagonist of the story, a man whose ordinary life as a convenience store manager is thrown into chaos when a series of bizarre events begin to mirror the apocalyptic stories he and his friends invented as children. As a boy, Kenji was a joyful and charismatic child with a vivid imagination and a strong sense of adventure. He was the driving force behind his group of friends, leading them to build a secret base and chronicle their fantasies of saving the world in what would become known as the "Book of Prophecy".

In adulthood, Kenji has abandoned his youthful dreams of becoming a rock star, having taken over the family liquor store and converted it into a supermarket to support his family. He lives a quiet, somewhat numb existence, his former passion buried under the daily grind of work and responsibility. A key part of his adult life is raising his young niece, Kanna, after his sister, Kiriko, disappeared. Despite his seemingly mundane life, Kenji retains his core ideals and a deep-seated, unwavering belief in justice.

Kenji's motivation is reignited when an old friend dies under mysterious circumstances, leading him to discover that a sinister cult leader known as 'Friend' is using their childhood Book of Prophecy as a blueprint for world domination. This revelation forces Kenji to confront his past and take a stand. His primary role evolves from a reluctant participant into a determined leader and the figurehead of a resistance movement formed by his former classmates. He is not a traditional hero with special skills but rather an ordinary man who is forced into extraordinary circumstances, driven by a need to protect his loved ones and put a stop to the nightmare he feels responsible for creating.

A deeply ingrained characteristic is his role as a determinator; once he commits to a path, he pursues it with incredible tenacity, never letting his fears get the better of him. He has a strong moral compass, preferring to defeat his enemies not through violence but through words or by exposing the emptiness of their ideology. This simple but powerful conviction is what makes him an inspiring, almost messianic figure to those who follow him. A pivotal aspect of his journey is his apparent death in a confrontation with Friend, after which he is assumed lost for many years. His eventual return, having survived and wandered while suffering from amnesia, marks a significant development, transforming him into a more weathered but even more resolute figure who becomes key to the final confrontation.

His relationships are the core of his character. He shares a deep bond with his childhood friends, particularly Choji Ochiai, known as Otcho, who acts as his loyal second-in-command. Yukiji Setoguchi, the only girl in their childhood group, shares a complex history with him and becomes a trusted ally and parental figure to Kanna in his absence. His most profound relationship is with his niece, Kanna Endo, for whom he sacrifices everything, and who carries on his legacy after his disappearance. Kenji's most notable ability is his talent for music. A skilled guitarist and songwriter since his youth, he uses his music not just for entertainment but as a powerful tool for communication and inspiration, creating a protest song, "Bob Lennon," that becomes an anthem of hope and resistance against Friend's oppressive regime.