Kasuga Arata lived a normal life in a small town, together with childhood friend and his cousin, Hijiri Kasuga. However, everything changed on the day of the Black Sun. The Breakdown Phenomenon which ruined the town where he took Hijiri away and resides was caused by the Black Sun. As Hijiri begins evaporating, she hangs a grimoire to his neck, requesting it to protect Kasuga. On losing all of his other friends as well as family and Hijiri distressed, Kasuga asks for his planet to be great again, which contributes to the grimoire artificially re-building his regular life, and making him forget the destruction of the town and Hijiri's disappearance. Lilith Asami, a mage, is sent to investigate the ruins and she finds the powerful spell within their stead. She makes Kasuga recall the specific events and hence the enchantment is broken, not without the grimoire telling him that Hijiri is not dead. Kasuga decides that his only alternative will be to become a magus himself therefore Hijiri could be rescued by him and he therefore joins a secret school for mages that copes with magic dilemmas all over the world, the Royal Biblia Academy. There he is introduced together with the Trinity Seven, seven powerful female mages who are at the top of the respective disciplines (Lilith being one of them) who will aid him in his aim to become a strong wizard and discover the truth about Hijiri along with the Black Sun. He soon discovers that another of the Trinity Seven, Arin, looks almost exactly like his lost cousin although she shows a wholly different character.