Mitsuko Takayanagi is a married woman in her early thirties who relocates from Tokyo to her husband Ichiro's rural village after several years of marriage. She mothers a young daughter, Aya, also called Achan. Ichiro's family holds near-total control over the village, yet Ichiro neglects Mitsuko and their child, leaving her isolated and emotionally deprived.

Mitsuko possesses notable beauty, characterized by purple hair—described as shoulder-length or waist-length—often tied in a ponytail with bangs, and brown eyes. Her personality blends politeness, kindness, and naivety with submissiveness and a strong sense of duty as wife and mother. She is caring, honorable, and respectful toward family, traits that heighten her vulnerability within the household.

Her trajectory shifts when she bathes her father-in-law, Tomizo. He exploits this act to blackmail her into sexual compliance, initiating her role as a sex object for multiple male relatives. Tomizo manipulates Mitsuko's marital neglect and loneliness, eroding her initial resistance. Over time, she develops an addiction to the physical encounters, increasingly craving interactions with her brother-in-law, Kouji. Mitsuko's journey transforms her from a dignified housewife to a woman recognizing herself as a sex slave within the family structure.

Her circumstances expand to involve other relatives, including Tomizo's wife Sumie, though specifics of Mitsuko's direct involvement remain undetailed. By later stages, she engages in multiple illicit relationships simultaneously, fueled by compounding physical addiction and emotional desolation from her husband's indifference.