Toji Nakahara fatally shot Kazuhito Harumi during a café robbery when Kazuhito intervened to protect another customer. After the killing, Toji occupied Kazuhito's abandoned apartment. There, he discovered and avidly read novels by Kirihime Natsuno, especially the "Deadly Sins" series, developing a strong admiration for her work.

He incorporated elements from Natsuno's fictional characters into his own combat methods, utilizing the thick "Deadly Sins" volumes as improvised weapons and armor during fights, demonstrating resourcefulness and deep familiarity with the material.

Natsuno eventually tracked Toji down, leading to a direct confrontation. After their battle, she left him hanging from a bridge. She then encouraged Kazuhito, who had been reincarnated as a dog, to take revenge. Kazuhito chose mercy, sparing Toji's life, partly recognizing their shared appreciation for literature. Following this act of mercy, authorities promptly arrested Toji.