Fujiyama Shinobu, a down-on-her-luck woman in her thirties, is having serious money problems. To make ends meet, she works as a low-level villain under the alias Sexy Fujiyama, a general for the so-called Flower Bud Gang, a criminal organization dedicated to harvesting Bondnergy by forcing innocent civilians into various forms of bondage gear. Her plans are constantly thwarted by the city's cheerful and devastatingly powerful protector, a ten-year-old magical girl named Princess Mamu. In a stroke of terrible luck, Mamu moves into the apartment next door to Shinobu, remaining completely unaware that her new neighbor is actually her arch-nemesis.

Seeing this as an opportunity to get a raise by finally defeating the magical girl, Shinobu resolves to befriend Mamu to learn her secrets and weaknesses. The story primarily follows their absurd domestic life together, as Shinobu’s schemes inevitably backfire in humiliating fashion. Whether she is trying to pry information out of the child, spy on her, or simply treat her to a meal, Shinobu usually ends up broke, injured, or stripped of her clothes. Despite being a villain by trade, Shinobu has a kind heart, and a genuine, if unintended, bond begins to form between the lonely adult and the seemingly perfect magical girl, who appears to live alone and craves a familial connection.

The setting is a comedic parody of the magical girl genre, focusing on the mundane interactions between the villain and the hero rather than epic battles. The Flower Bud Gang serves as a source of bizarre world-building, where the primary requirement for membership is looking good in a dominatrix outfit. The cast includes Shinobu's co-workers: her snarky underclass rival Canola, who is only in the gang to support her sick mother; the enthusiastic new recruit Sakura, who joined because she thinks evil is cool; and their leader, Big Flower, who seems more interested in dressing up her employees than in world domination.

Several narrative arcs develop from this premise. A major early storyline begins when Shinobu discovers Mamu is her neighbor, setting the stage for their entire relationship. Another significant arc involves the introduction of a second magical girl, Camelia, whose arrival creates further chaos for Shinobu. Later chapters explore Shinobu’s attempts to train a new villain recruit, and storylines such as the Crane Game Incident lead to Mamu gaining enough trust in Shinobu to remove her mask while they are together, indicating a genuine character progression away from being a simple gag manga. The comedy often stems from the contrast between Mamu’s terrifying, superhuman strength (kicking cars across parking lots) and her innocent, childlike obliviousness to Shinobu’s transparent scheming, all while Shinobu suffers from constant, cartoonish violence and financial ruin.