My childhood friend, Marin, lives in the same apartment building. She's incredibly cute, always wearing short skirts, and I couldn't help peeking up her skirt from the bottom of the stairs. As punishment, she demanded I let her use an electric massager on me for just 10 seconds. Thinking I could endure that long, I agreed. But the vibrations were far more intense than expected, and I gave in almost instantly, failing to last even 10 seconds. Angry at my weakness, she imposed an unfair penalty game—she handcuffed me, face-sat on my mouth, and began a long, merciless electric massage session. Under the beautiful Marin's relentless treatment, I couldn't hold back and ended up ejaculating, though I thought she hadn't noticed. When I defiantly said, "There's no way I'd cum from something like that with you," she innocently pulled out a large massage device and said, "This feels super ticklish after you've already come, you know?" Then she began her interrogation: "I won't stop until you admit you came!" My oversensitive cock, freshly spent, was tortured again and again, forced to climax multiple times. She didn't stop even after each orgasm, continuing the electric massage on my hypersensitive member until I was forced to confess aloud that I had come—completely dominated by the merciless older sister, Marin.