On August 10, I went alone to the river to enjoy some fishing. Then, an unfamiliar older sister approached me and invited me to play together. We started playing with water guns, getting each other completely soaked. Eventually, the older sister took off her clothes and began swimming in the river. Afterward, I went to her house where we played games and pretended to wrestle. Soon, we began playing by touching her breasts and buttocks, and during this, my friend's penis became erect. In that state, the older sister rubbed and licked his penis, causing white liquid to come out. Seeing this, I felt a bit frightened and quickly returned home with my friend.