My girlfriend has no interest in sex at all. I thought I could stay over at her house this weekend and have loads of fun... But from the looks of it, I guess we'll just watch movies and play games...' Then, my busty sister, the complete opposite of my girlfriend, comes home. My eyes are drawn to Yuka, who is leaning forward and blowing air into her blouse with a fan. Yuka then takes a photo of me staring at her breasts, and since then, I've been spending every day engaging in naughty acts with my sister, betraying my girlfriend...