That day, when I was back home, she had sex with her extremely sexy best friend at home, and she had been cumming and running around in multiple places.

Mizuki, the girlfriend of her best friend, is so cute that she's jealous... and happens to peek at her while having sex, and learns about the point that Mizuki screams "That's it" - her weaknesses of being sensitive to cum. I want to take that sensitive body into something too! Unable to contain her desire, she decides to make her best friend's girlfriend cum while her best friend returns to her parents' house and is away! At first, she forced herself to commit, but as she delves into her weaknesses accurately, she gradually begins to ask for it.