Ayumu Aikawa, a 16-year-old high school student living alone due to his parents' constant travels, met a brutal end when a serial killer murdered him, impaling him through the body with a katana while he investigated suspicious activity. Briefly acquainted necromancer Eucliwood Hellscythe resurrected him as a zombie, binding him to her as a servant. This undeath granted Ayumu functional immortality, rapid regeneration, and superhuman strength exceeding human limits, though exposure to sunlight inflicted severe dehydration and desiccation. Forced to search for his killer while maintaining a semblance of normal life, Ayumu encountered Haruna, a Masou-Shoujo (Magical Garment Girl), battling a bear-like Megalo during a nighttime cemetery investigation. Haruna bisected him with her chainsaw, Mystletainn, but his zombie nature ensured survival. When Haruna attempted to erase his memory of the event, her powers backfired, transferring her magical abilities to him instead. This compelled Ayumu to assume her role in fighting Megalos, necessitating a transformation into a Masou-Shoujo—complete with a pink, frilly outfit and wielding Mystletainn, a source of deep embarrassment. While this transformation temporarily negated his sunlight weakness, it exposed him to public humiliation, mitigated only by his acquired ability to erase witnesses' memories. Ayumu's household grew when Seraphim, a vampire ninja seeking to serve Eucliwood, challenged him after the necromancer's rejection. Defeating her in combat led Seraphim to become his nominal servant, though she persistently insulted him as "maggot" or "dung beetle." Later, his classmate Orito introduced him to Kyoko, a hospital patient and fellow victim of the serial killer. Ayumu uncovered Kyoko as the killer, culminating in a brutal confrontation where he nearly eliminated her with Mystletainn. He ultimately spared her final life after she begged for mercy, hoping she would reform. This event highlighted his capacity for vengeful aggression during conflicts, contrasting sharply with his typically passive demeanor. Personality-wise, Ayumu exhibited a lazy, weak-willed disposition in daily life, frequently daydreaming about Eucliwood in imouto-themed fantasies where she called him "Onii-chan" and made playful requests—a habit Eucliwood knowingly acknowledged. Yet under threat, he transformed into a decisive, morally grounded fighter, exemplified by battles with adversaries like Kyoko and Yoruno, a powerful zombie. Despite his ferocity, he consistently prioritized mercy and ethical resolutions, withdrawing from violence when alternatives such as Eucliwood's intervention emerged. Comedic misfortunes often arose from accidental perversion, triggering frequent physical punishments from Haruna, Seraphim, or vampire ninja Mael Strom. Multiple female characters—including Eucliwood, Haruna, Seraphim, Sarasvati, Yuki, and Kyoko—developed romantic feelings for him, though no relationship formalized by the story's conclusion. Throughout his journey, Ayumu faced possession by Belphegor, the demon of sloth, following memory erasure—a manifestation of his deep-seated desire for tranquility. By the light novel's conclusion, he transitioned back to humanity, working as a 25-year-old salaryman while cohabiting peacefully with his female companions.