Namikoshi appears in Rampo Kitan: Game of Laplace as a middle‑school classmate and the closest friend of the brilliant detective Kogoro Akechi. He is the original creator of the Dark Star formula and the first person to take on the identity of the vigilante known as the Fiend with Twenty Faces. His background is marked by severe physical abuse at the hands of his father and persistent bullying at school, including being cut with a knife by classmates. This sustained suffering led him to develop the Dark Star algorithm, a mathematical system intended to predict and eliminate individuals he considered social evils. Using it, he killed his bullies, his teacher, and his parents. Despite these actions, Namikoshi was initially described as a kind and hardworking boy who desperately sought Akechi’s acknowledgment. His personality blends a gentle, almost fragile demeanor with a merciless conviction when pursuing his vision of justice. He is highly analytical and introspective, driven by a desire to prove that the dream he and Akechi once shared of completing the Dark Star was not an illusion. His motivations center on changing the world through a logical elimination of perceived corruption, and he views Kobayashi as a potential successor or catalyst for his final plan. Namikoshi’s role in the story is that of the originator of the Twenty Faces phenomenon and the emotional core of the series’ climax. His relationship with Akechi is complex: they were once inseparable collaborators, but their bond fractured under the weight of trauma and conflicting ideologies. Namikoshi becomes Akechi’s rival, forcing him to confront the consequences of their shared past. After a failed suicide attempt that Akechi could not prevent, Namikoshi eventually returns to orchestrate a city‑wide ideological crisis, compelling Akechi to acknowledge his vision. His development traces a tragic arc from a victim of abuse to a calculating mastermind, culminating in a final confrontation that determines the legacy of the Twenty Faces. His notable ability is the creation of the Dark Star formula, a mathematical tool capable of predicting human behavior and identifying targets for vigilante justice.