My sister came to stay in my small one-room apartment in Tokyo where I live alone. I slept on the futon, and she slept on the sofa... Late at night, I woke up to find my sister sleeping soundly in her underwear! Excited by my sister's transformation into a woman, I began to masturbate, touching her vulva over her underwear, when suddenly she turned over in her sleep! Oh no! She's going to find out! In a panic, I hid my penis and dove under the covers, but it was already too late...
