When my parents remarried, I went on a hot spring trip with my new family. I shared a room with my unsuspecting stepsister, despite her large breasts! However, I was invited to shower with her in the private bathroom. While I was excitedly washing my sister-in-law's body, when she asked me to wash her back, I said, "Brother… something is hitting my back." His penis was very erect and stuck together. On my sister-in-law's back! Naturally, I noticed and thought that was the end of it… But later, my sister-in-law was aroused by my erect penis and invited me to ejaculate three times in a row. Without pulling out, she didn't resist; instead, she experienced vaginal spasms—a divine development!