Shun Asanaga, a 15-year-old junior high school student, discovers a mysterious crystal in his father's office, which leads to his transportation into the world of Endra. There, he meets Emilio, a prince who is nearing his 16th birthday and seeks revenge against King Delzain, who has imprisoned him. Emilio's capture was a result of his lack of strength at the time, but Shun's arrival in Endra sets him on a path to complete Emilio's revenge, while also trying to find a way back home. Shun's presence in this foreign world creates a complex dynamic between the two boys from different backgrounds.
