After her husband, Taizo, loses his job and returns to his family home, Eri Hosaka struggles to adapt to her new life. Her sister-in-law, Rion, warmly welcomes them, but her brother-in-law, Shuichi, harshly demands that Taizo find work immediately. Eri feels lost, unable to understand the family's strict customs. A few days later, while doing laundry, Eri accidentally discovers Rion secretly meeting with her younger brother-in-law, Ryoji. Shocked and frozen in place, Eri listens as Rion calmly explains the family's hidden tradition—one that awakens something unexpected within her. As secrets unravel, a story of family bonds, forbidden desires, and humiliation begins to unfold.