Asagi has a dream about being a capital-H Hero who fights the Final Boss/Desco and encounters her evil twin.

She wakes up, decides that obviously that would never happen to a Normal High School Girl? like her.

Then she is immediately summoned by Freya from Ragna Quest who tells Asagi that she's secretly a Goddess who must save the multiverse by gathering heroes to fight for Justice. And also because Freya's too lazy to do it herself.