Mina-san, my older sister-in-law, came to do housework for the three days my parents were away on a trip. I can't help but be bothered by her big ass squeezed into tight, firm jeans, whether she's cleaning or cooking... And the thong that's digging into her ass is always sticking out! Unable to endure it, I push her down and furiously piston-fuck her from behind, and that erotic ass shakes and jiggles, it's too amazing. After cumming and calming down, I panic, realizing I've done something terrible, but Mina-san seems to have her libido ignited, and she's teasingly showing off her thong and inviting me...!