During Itsuki's senior graduation ceremony, his cousin Mahiru confides that she is expecting a child. At that instant a luminous portal opens, carrying them both into the distant mysterious realm of Granvania. In this domain, 'Impurities' have been disrupting the everlasting celestial Stars, driving Granvania into deep unending turmoil and chaotic looming disarray. Itsuki is discovered to be destined to encounter the revered 'Star Maidens,' positioning him as Granvania's final salvation; he is tasked with birthing powerful 'Star Children' and fighting the relentless 'impurities.' Failure to finish this perilous mission could prevent his return home for the future forever.
