Yuka marries her junior colleague, Kenji, and begins a new life together as a newlywed couple. Kenji's family consists of his father and older brother, and with her cheerful and intelligent personality, Yuka brings a refreshing light into their previously gloomy household. Her father-in-law sheds tears of joy, filled with hope for the future. However, her brother-in-law, Shuichi, is a reclusive man who develops an abnormal fascination with Yuka's beauty. Though unsettled by his behavior, Yuka continues to treat him kindly. One day, after being drugged with an aphrodisiac, Yuka is raped by Shuichi. Though she initially feels intense disgust, she is shocked by his enormous penis and unexpectedly overwhelmed by pleasure—soon craving it herself. From that moment on, Yuka becomes deeply entangled in a forbidden relationship with her brother-in-law.