My wife is pregnant and has returned to her hometown, so her sister came to our house, thinking that she must be in trouble. But in reality, her sister is not getting along with her husband and is sexually frustrated, so she took advantage of her younger sister's return to her hometown to come to our house to relieve her sexual frustration. Not knowing this, I was taking a bath and suddenly my sister came in and said, "I'll wash your back," and asked, "Aren't you pent up?" I tried to resist her, but...