Until the morning with her younger sister, who was refugee home from a sudden heavy rain...

The man who lives with her was thinking about getting married. She also noticed a good relationship with her younger sister Sachiko. One day, a sudden heavy rain stopped the train and her sister was refugee home, and she came to her nearby sister's place of living together. However, she is stuck at work and is refugee home, leaving her alone with her step-sister, Sachiko. When Sachiko invited her in, her whole body was soaked and her underwear was see-through, and she felt a woman she didn't normally feel and lost her rationality, causing her to steal her lips.