I'm a virgin who's feeling down after failing my first sexual encounter with my girlfriend. My kind big-breasted sister can't stand to see me like that, so she uses her own body to encourage me by asking, "Do you want to practice on my body?" But she says, "Sex is like having sex with your beloved girlfriend..." and we start with a bare-knee massage. But as I rub her pussy, it gradually gets wetter. I can't stand the pleasure and start moving my hips... In the end, I insert my penis raw and cum inside her, and instead of getting angry, my sister cums three times in a row without pulling out!