On graduation day, Itsuki's cousin Mahiru tells him that he is pregnant. At that moment, a gate of light appears and transports the two to the world of Granvania. In this land, "Impurities" have caused a disturbance to the Stars, plunging Granvania into chaos and disorder. And Itsuki, now revealed as someone destined to meet the "Star Maidens", is seen as Granvania's last hope and therefore given the task of producing "Star " and fighting the "impurities". And unless the task is completed, Itsuki will never be able to return home.

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