Based on the school action role-playing game COLOPL. The year is 2045. The planet has been tainted by Irousu (mystery invaders that come out of nowhere), and humanity are now constrained and controlled. Ordinary females worldwide are defying the invaders, despite the lack of a formidable army or even firearms. The Shinjugamine Girls Academy is a training ground for these "Hoshimori" (Star Guardians) who will combat the Irousu. The player has been appointed to this institution in order to train the girls and reclaim the damaged Earth. As a result, the bells reverberate across the sun-strewn schoolyard once more to signal the start of lessons today...