The story begins in Astrub, where the young Sacrier Pym Eoliath studies magic at the Grilembore school. Being new at the school and far from a model student, he is frequently sent to detention and gets into trouble with other students, although he also has a few friends, among which Wendy, Fuliduli and Fistule, a friendly ghost looking for a way to reincarnate.
His life changes the day he accidentally teleports into the Hormonde, a dimension inhabited by the Hour Demons. He discovers that the Demons have built arenas there and kidnap various people to fight in them for their entertainment. But unlike those people, Pym has the ability to teleport back to the World of Twelve and returns shortly after, crash-landing into the principal's office. Principal Krokker and two of Pym's teachers take this opportunity to discuss his poor record at the school, which is especially appalling considering he has only been there for a month. They decide to search his thoughts using a magic device in the hopes of finding out the root cause of his bad behavior.
In the process, they discover that he has seen Hour Demons in person, which is alarming as they know that these Demons shouldn't be in the World of Twelve. One teacher, Lethaline Sigisbul, also notices that Pym saw her briefly in the Hormonde, but manages to hide that memory from the others. Acting as a double agent for the Demon Midnight, she is worried about Pym finding out too much about her and becomes wary of him. When Krokker and the teachers discuss putting Pym in isolation for everyone's safety, Pym overhears and immediately runs away, spending the next few days practicing his teleportation spell and hiding from everyone.
While the entire school is set to finding him, he comes into possession of an odd manga that shows scenes from the arenas, including characters he met on his recent trip. He finds that odd since the manga is supposedly ten years old, yet the characters appear exactly the same as he saw them. He deduces that these people were taken from the World of Twelve and begins thinking that he might find his missing family members in the Hormonde, even though they disappeared years ago. Taking example after the gladiators depicted in the manga, he decides that he needs to acquire a powerful weapon and become a champion of the arenas.
Immediately following that newfound life goal, Lethaline finds him in the streets of Astrub and seems intent on dealing with him, but by then he has realized that the woman who looked familiar in the Hormonde was none other than his teacher. He manages to escape her grasp by teleporting back to the Hormonde... and lands right in the middle of a fight in an arena, where his gladiator friends met during his first incursion are fighting a desperate match only meant to entertain the Demon XVII. He decides to help out and realizes that the situation looks almost identical to one seen in the manga he now carries with him. On the spur of the moment, he decides to imitate the strategy of the character Wyd Krad, a Sacrier who was caught in the same predicament, and manages to buy his allies some time. As this first volume concludes, he has taken a bad hit, but his Sacrier powers, dormant until then, unexpectedly awaken, allowing him to rejoin the battle.