Going on a hot spring trip with relatives, my heart raced at the sight of my grown-up sister's lewd body. I caught her masturbating in the bath and she licked my semen saying 'I'll teach you about a woman's body.' She showed me her pussy in the bathtub, and as we washed each other, my dick got hard again. My sister also pretended to wash my cock but was actually gripping it and moving it lewdly, making me excited. As we rubbed our bodies together, I couldn't hold back any longer and slipped it in.
