Brother-in-law Hiro is unemployed and living with his older brother and sister-in-law Yuka Aoba. One day, an intoxicated stranger vomits on him, ruining his clothes. The man demands an exorbitant dry-cleaning fee, leaving Hiro unable to pay. Stepping in to help, Yuka offers to wash the clothes. However, the man becomes aroused by Yuka's voluptuous figure and starts harassing her under various pretexts, teasing and provoking her. Though she resists, Yuka's sensitive body gradually responds to his advances. Witnessing the scene, Hiro finds himself overwhelmed with desire for his sister-in-law. The story unfolds through shifting relationships and emotional turmoil, exploring themes of temptation, infidelity, and forbidden lust.