[FNS-176] I Became a Masturbation Partner for My Girlfriend’s Busty Unemployed Older Sister Rin

I never thought I’d be jerking off to my girlfriend’s older sister, but here I am, balls deep in my own hand while Rin’s massive tits bounce in my face. She’s a NEET, just lounging around the house in her skimpy clothes, and I can’t help but watch her every move. Her huge butt fills out those tiny shorts, and when she bends over to pick something up, I lose it. I’m supposed to be loyal to my girlfriend, but Rin knows exactly what she’s doing. She catches me staring and just smirks, spreading her legs wider as she lies on the couch, her fingers sliding into her wet pussy. She moans my name, and I’m done for. I pull out my cock, already hard and leaking, and start stroking to the sight of her masturbating. She tells me to cum for her, and I do, shooting my load all over my stomach while she laughs. I’m a cuckold to my own girlfriend’s sister, and I love every degrading second of it. Her tits are so big, I can almost feel them in my hands as I imagine fucking her. But she never lets me touch, just watches me stroke myself to her body. I’m addicted to the humiliation, and I know I’ll be back tomorrow, cock in hand, ready to worship her again.