My serious little sister was completely absorbed in her club activities, with morning and after-school practices every day. But now, she's retired. While she used to relieve stress through her club, she's become a shut-in since retiring. When I peeked into her room, she was masturbating intensely and cumming over and over! Did all that excess physical energy turn into an uncontrollable sexual drive? When I was caught peeking, I hurriedly apologized, but she acted strange... It turns out she directed all that unsatisfied libido toward me! I'm drenched in sweat as she pushes me to the limit, making me cum repeatedly. She's completely wearing out my cock, and I'm not even athletic—my stamina is below average... Please, give me a break!