I was passing by the bathroom when I heard soft moans. Curiosity got the better of me, and I peeked inside. There was my half-naked step sister, sitting on the toilet, using a hygienic water stream to masturbate. Her eyes were closed, her head tilted back in ecstasy as the water jet hit just the right spot. The sight was unbelievably hot. I couldn't tear my eyes away as she writhed and moaned, completely lost in pleasure. The whole scene was so taboo and wrong, but that just made it even more arousing. I stood there, hidden, watching her until she finally finished with a shuddering orgasm.
