On a family trip, I took a bath with my sister for the first time in a while, and her beautiful big breasts were bigger than I imagined, and I got a full erection! I tried desperately to hide it, but she found out I was still a virgin, so I decided to beg her to let me do it, since I was going to be embarrassed anyway! My sister took pity on me, even kneeling down, and reluctantly agreed. I enjoyed losing my virginity while rubbing her big breasts!