https://comic.pixiv.net/works/2331

Two girls who want to become idols are entering into their long dreamed school—Kiraboshi-juku—Kiraboshi Nadeshiko and her close friend Mangetsu Sakurako. These two are so close that despite both being girls, they're often compared to a married couple by people around them.

And so begins their life in the dormitory as roommates. However, on their first night, an unusual, illicit impulse strikes Nadeshiko...