Things have been looking sunny for Arata Kasuga lately. Unfortunately it's been the wrong sun in the sky, and the mysterious Breakdown Phenomenon that accompanied it destroyed his town and stole his beloved cousin Hiijiri, leaving Arata in a fantasy world of his own creation! There's still a chance to save her, however, as the appearance of the Black Sun also revealed Arata's potential abilities as a mage, placing him in the powerful Demon Lord class.