『Customs, traditions, lineage, social status. Matters that are beyond human control, that is what humans call fate.』 Magic and many different species exist in the world of Inglens. In this world, when humans turn twelve years old, they undergo a ritual to summon a familiar called a Nightmare. A Nightmare is a friend, and a partner. They are conscious beings who are more than simple familiars, they are knights who fight for their master’s happiness. Such non-human life forms have lived closely together with humans in their daily lives. In the village of Avalon, a girl named Eris also performs this ritual. The familiar that answers her summons belongs to only her, is driven by her will, and he is a beautiful boy. The boy’s name is Arthur, and he claims to be a knight who will protect Eris. That is how they begin to live together. Furthermore, a messenger from the kingdom of Graceville, a country which boasts the world’s best technology and culture, came to tell them that Arthur is special among the Nightmares, that he is one of the Original Nightmares, and he is known as the 「King of Knights.」 And then, after a series of events, they are asked to enroll in a certain Magic Academy in Graceville Kingdom—- 『Beside the one who follows, or defies, her fate, is the one standing there a dream or reality?』