I went on a hot spring trip with my relatives and was excited by my older sister's lewd body that has grown into an adult. She found me masturbating in the bathroom and licked my semen and said, "I'll teach you about a woman's body." She showed me her pussy in the bathtub and while we washed each other, my dick started to swell again. My older sister also pretended to wash my dick, but she grabbed it and moved it lewdly, getting excited. As we rubbed our bodies together, I couldn't hold back and slipped it in.