I don't remember what started it, but my sister and I had a romantic relationship since our school days. We did it many times in secret from our mother until we both got boyfriends, but gradually my sister started to dislike it. However, my sister's nipples were sensitive, so when she wasn't in the mood, I would tease them and she would become compliant. She was always indulgent towards me, her younger brother, so I continued to sleep with her until I was satisfied... But then my sister left home for work...