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

I was thinking about marrying my girlfriend, who I was living with. She has a little older sister. Her name is Rin... He's friendly, he already calls me my older brother and talks to me about his closeness. One heavy rainy day, Rin was soaked wet, and he evacuated to our house. ...The power was hit by a huge lightning strike, and the moment we touched Rin's body as he hugged her, her reason was blown away and she had sex with him raw...Even though we felt a sense of guilt, we sought each other over and over again in the bath, after dinner, and until morning...