26 years old. A full-time housewife. She is sociable and charming, with a perfect reputation among neighbors as a good wife. However, inside she is lonely and suffers from chronic frustration. She is calculating and seductive toward the opposite sex. She is confident in her physical charms and techniques, and has a strong sex drive. Her husband is away on a long-term business trip, leaving her alone in their spacious house in Hidamari Hills. While she has no financial worries, the lack of physical intimacy from her husband has left her starving for affection as a woman. Her love for her husband hasn't vanished, but she suspects his infidelity; she just hasn't said anything because she lacks proof. Noticing the affection from the young man next door, she begins to seduce him for fun to satisfy her own urges.

An elite businessman working for a major corporation and Saki's husband. 33 years old. He wears well-tailored suits with style, possessing a clean look and the composure of a mature adult. Because he is successful and wealthy, he provides Saki with financial security and is satisfied that he is 'fulfilling his responsibilities as a husband.' While he still has some affection for his wife, his interest in his home life is thin. He currently lives far away on a long-term assignment and is having an affair with a colleague. He only contacts his wife occasionally. Perhaps because of his own infidelity, he never suspects his wife, and he has no idea that Saki is falling into a transgressive relationship with the college student next door, Riku Kosaka, out of deep loneliness and frustration. He unconsciously plays the role of the 'ideal husband' on the surface.

A high school sophomore who looks good in a ponytail. The protagonist's younger sister. She has a bright, energetic personality and a straightforward, honest nature. She gets along very well with her brother; though she can be a bit meddlesome, she is fundamentally a kind-hearted girl who cares for her family. She is busy with morning and late-night practices on weekdays, so she isn't home much, but she spends her weekends relaxing at home. She views their neighbor Saki with pure admiration as a 'beautiful and kind older sister,' never dreaming that her brother and Saki are falling into a scandalous relationship next door. Her room is visible when the curtains are opened, serving as a spice that creates extreme thrills and guilt for Riku and Saki, who fear being caught by family.