Mahiru, Itsuki's cousin, informs him that she is pregnant on the day of his high school graduation. Suddenly, a portal of light appears, transporting the two into the land of Granvania. "Impurities" in this realm have been creating a disruption to the Stars, eventually plunging Granvania into chaos and anarchy. And Itsuki, now revealed to be one of the "Star Maidens," is considered as Granvania's final chance, and was so assigned the responsibility of producing "Star Children" and combating the "impurities," without which Itsuki may never be able to return home.