A night alone with my brother's wife

After his parents passed away, his older brother and wife Ayumi live in his parents' house. I used to come here a lot, but one incident caused me to move away from my parents' house. Even though I was drinking, I betrayed my brother. One day, Typhoon No. 19 was hit directly. While being hit by a heavy rain, I went to my parents' house, intending to take shelter from the rain. However, that night, the train stopped and my brother couldn't get back from work, so on his way home from shopping, he was alone with Ayumi, a wet braless woman...