During a hot spring trip, I was caught jerking off using my sister's naked body as visual aid in the mixed-gender open-air bath. I got a big scolding… I truly apologized, and when she saw my erection, my loving sister said, 'Since we're siblings, we can't actually insert it, but we can just rub...' So we started with dry humping! Then I slid right into her wet pussy for real penetration! Of course, I didn't stop and finished inside!
