Kakeru Satsuki has been living a boring, ordinary life ever since his sister committed suicide seven years ago. However, one day, he and his best friend Yuka Minase are suddenly transported to an alternate reality where the sky is filled with dark, crimson clouds, a black moon and terrifying creatures lurk.

Kakeru and Yuka are in the Red Night dimension again and this time they meet a strong young woman named Misuzu Kusakabe, who saves them from a horde of the evil blob like creatures, and find a girl trapped in a crystal. They are attacked by some other strong creatures and then find themselves back in the normal world. Can they discover the mystery behind the Red Night and why only certain people are taken there?

Kakeru asks Misuzu if she will teach him how to use a sword and she refuses. He is determined to learn so he can protect Yaku the next time they are taken to the Red Night. Can he master the sword before then?