Yui, who used to work at a foreign automobile dealership, eloped three years ago with a married male customer at the time. He possessed warmth, affection, and consideration as a father figure—things missing in his previous marriage—making him Yuki's ideal man. Unexpectedly, however, his ex-wife's daughter came to live with them as part of the new family. From the beginning of their marriage, the three of them started living together. While Yui had anticipated some resistance from the daughter, the girl’s intense jealousy soon turned into open hostility despite being only 17 years old. Moreover, she began deliberately interrupting moments when Yui and her husband were alone, asserting herself as a romantic rival. While Yui strives to protect her bond with her husband, she suffers emotionally from his dismissive attitude toward the daughter’s behavior and grows increasingly tormented by the girl’s persistent interference. Though she tries to understand, Yui’s suppressed physical desires intensify, eventually pushing her into an irreversible, desperate situation.