My cousin Koharu-chan, who I used to play with a lot when I was little, has become a working adult and started living alone. She invited me to come over and I wanted to see her again, so I decided to go to her house during summer vacation. It's been seven years since we last met, and I'm excited to see that she's grown up and become a beautiful, grown-up woman... but she still treats me like a little kid, with the same distance between us as she did back then. I'm still at my age, and I get excited when a beautiful woman approaches me... and I have to break my promise to my sister...