Koharu Nishio, 46-year-old housewife. Married for 21 years and mother of two, she decided to participate in this project seeking a rare chance to experience something sensual again. Introduced by a friend to a stylish and cute pink vibrator—"These days, toys like this are all the rage"—she became deeply fascinated, opening up a whole new world of masturbation. Thanks to her daily self-training routine, her libido remains strong and satisfied, allowing her to live a fulfilling life despite having no sexual activity with her husband for the past three years. Yet this secret pleasure, hidden from her spouse, has become a source of personal pride and stubborn independence. She feels embarrassed to actively desire sex and refuses to voice it aloud. How will she climb the evolving staircase of pleasure—from masturbation to real intercourse?