I went to my sister's house to take care of something, but she was in the middle of changing. I panicked, but I ended up getting a rock hard erection in front of my sister. I thought she would be put off, but instead she came to me with a smile and asked, "Hey, what's this? Hey, can you explain to me?" She knew what I was talking about, but she came to me and started playing with my dick. So I let my sister do what she wanted, and she made me cum with the techniques of a prostitute. All 6 chapters.