Mao is a plain, chubby young woman who loves gardening and works an ordinary job, but her life falls apart when she is suddenly fired and then swindled into taking on a heavy debt. On the verge of despair, she is rescued by Kurosaki, a strikingly handsome butler who works for a powerful wealthy family. He proposes a fake marriage contract, and Mao, with few other options, agrees.

Under the pretense of being Kurosaki’s wife, Mao moves into a grand mansion owned by the family’s young master, a charismatic and somewhat spoiled heir. Kurosaki, the head butler, presents Mao with elegant clothes and makeup, and she undergoes a dramatic physical transformation, losing weight and becoming a beauty. Her previously indifferent coworkers start treating her differently, and she becomes popular in the mansion. However, the contract marriage is not purely for show—Kurosaki reveals that Mao possesses a special, alluring voice that instinctively excites men, and that his true assignment is to use her as a tool to manipulate the master for some undisclosed purpose. This revelation shocks Mao and deepens the emotional complexity.

As Mao spends time in the mansion, she forms a bond with the young master, who begins to develop genuine feelings for her. He competes with Kurosaki for her attention, leading to a love triangle. The master’s mother, a scheming woman known as “Oku-sama,” also becomes involved, seeking to control events and pressure Mao into a marriage with her son to secure the family line. Mao struggles with her own growing feelings: she is drawn to Kurosaki’s cool yet passionate nature, but she also feels affection for the master’s earnest devotion. The situation grows increasingly tangled as Kurosaki’s hidden past and the master’s family secrets come to light.

The narrative arcs include Mao’s transformation from a downtrodden girl to a confident woman, the fake marriage gradually becoming real, and the master’s pursuit of Mao despite knowing her contract with Kurosaki. Key turning points include a fire set by the jealous Oku-sama that leaves Kurosaki with amnesia, Mao’s pregnancy, and a five-year time skip during which Mao raises a daughter alone while Kurosaki searches for her. The story culminates in a dramatic rescue when Kurosaki is caught in a landslide, prompting Mao to finally confess her true love and propose for real. The series concludes with the couple reuniting and the fake marriage becoming a genuine one.