In the medieval fantasy world of Alfheimr, succubus princess Astarotte Ygvar--the first princess of the kingdom of Ygvar--has just reached the age of 10. In the coming years, it is necessary for succubi to obtain a male harem. To maintain their appearance, they must consume a substance only found on males called "Sauzfryma", better known as semen.

The princess, however, detests males and will only agree to create a harem if a human male joins.

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...