From Comic-Walker:
I'm suddenly living together with the older girl I used to have a crush on. Even more, I'm starting to suspect that she's a slut? Naoto Kiyoshi is a young man who just entered university after failing his entrance exams one year before. When he was looking for a place to live in so that he could move to Tokyo, he found himself living together with Luna, a relative and older girl who he used to have a crush on.
The Luna he admired in the past was neat, beautiful and mature and now she apparently became a slut!? Night after night, he hears her seductive and unladylike moans, and it's making Naoto horny. There are also other men she's unreasonably close to besides him. Luna, whose thoughts he couldn't fathom is leading him around by the nose! Furthermore, other women with lewd quirks aside from Luna have also gathered there. This is the start of his exciting new life surrounded by slutty (?) older girls!