Nami Koishikawa served as a waitress in a maid café, her curvaceous figure often drawing attention—sometimes unwanted. Her uniform, ill-fitting due to her bust size, led to frequent mishaps like tripping and falling onto patrons. She initially saw her manager as well-meaning, unaware his actions might be deliberate.

Clumsy and naive, traits reportedly shared with her good-natured but foolish brother, Nami encountered a gravely injured woman one night after work. The woman entrusted her with a mysterious eye-patterned pendant, urging Nami to "take her place" before disappearing.

Curious about the pendant, Nami accidentally activated it during an awkward moment, triggering a transformation. She became clothed in a skimpy uniform as a "Sexy Sailor Soldier," gaining magical powers for fighting demons. However, the transformation drastically amplified her pheromones, driving nearby demons into frenzied sexual desire and alerting them to her presence. Unprepared and frightened, Nami primarily used her new abilities to flee.

Overwhelmed during her first demon encounter, she found herself cornered until reaching a skyscraper. There, her café friend Chisato Yamane—a veteran soldier—intervened to fight the demon. Despite Chisato's efforts, both were captured within a demonic portal alongside other demons. Nami freed them, and additional soldiers arrived to repel the pursuers.

Following this, Nami joined Chisato and three other warriors in their mission to hunt and eliminate sex demons.