The character Kakuta is introduced in the manga during its depiction of a dystopian future. By profession, he is a manga artist, a calling that defines his identity and his fate. He is portrayed as a mild-mannered and unassuming individual, a hapless everyman who seems unsuited for the dangerous conspiracies he is thrust into. His defining trait is his all-consuming passion for his craft; he is determined to become a famous manga artist and constantly views the world around him as potential source material for stories.

Kakuta’s central role in the story begins when he is arrested and sentenced to life imprisonment for publishing a manga that the ruling regime, the Friend organization, deems subversive and dangerous. He is sent to Umihotaru Prison, a high-security facility built on a man-made island in Tokyo Bay. Upon his arrival, he is placed in solitary confinement, where he becomes the cellmate, and eventual partner, of the enigmatic and fearsome prisoner known as The Monster. This prisoner is later revealed to be Otcho, one of the original heroes from the protagonists' childhood and a key resistance figure.

The relationship between Kakuta and Otcho is a crucial element of his character development. Initially, Kakuta is fearful and out of his depth, aware of his physical limitations and seemingly helpless against the prison system. However, through his interactions with Otcho, he finds unexpected strength. Together, they orchestrate a daring escape from the island prison, swimming ten kilometers to the mainland. During this ordeal, his artistic nature briefly surfaces, as he becomes momentarily distracted by the dramatic potential of their escape, forcing Otcho to refocus him on survival. This partnership transforms Kakuta from a passive victim into an active participant in the resistance. After escaping, he joins Otcho in the search for a former classmate named Dr. Yamane, a quest that leads them back to their old neighborhood in an attempt to uncover more secrets about Friend's true identity.

Kakuta’s primary motivation evolves from a personal desire to survive and pursue his artistic dreams to a broader commitment to uncovering the truth. His ambition to create a manga about everything he learns regarding the conspiracy, particularly concerning a character named Ami (or Friend), gives his journey a unique purpose. He is depicted as perhaps the most authentically human character in the series, representing the ordinary person who is punished by an unjust system and who, despite being in the wrong place at the wrong time, rises to the occasion to snatch victory from defeat. His notable abilities lie not in combat, but in his keen observational skills as an artist and an unwavering, almost childlike, dedication to his art, which ultimately proves to be a form of quiet resistance.