Upon hearing news of their father's passing, Reiko Yamaguchi and Saki Aikawa—half-sisters with different mothers—meet for the first time at the house where their father spent his final days. Their father's last wife, Sumire, warmly welcomes the two sisters. That night, Reiko visits Saki, confessing an overwhelming loneliness and asking to sleep together. The two instinctively draw close, lips meeting as their bodies intertwine, deepening their bond. In the aftermath, driven by a desire to confirm whether Sumire truly loved their father, an unexpected new relationship begins to unfold.