Surrounded by her husband and son Shuichi, Reiko lives a happy daily life. One night, she receives a call from her husband saying he's been in an accident. Fortunately, he's not in danger, but he's ordered to rest at home. A few days later, moved by his wife's careful nursing, her husband becomes aroused. Reiko accepts his cock in cowgirl position, a posture they rarely use. The intense pleasure of being on top, straddling her man, captivates her completely. Awakening to sensations unlike her ordinary routine, Reiko finds herself increasingly addicted to the cowgirl position.