The story is set in the 15th century, during the Hundred Years' War between France and England over the succession to the French throne. Montmorency, the son of a noble, immerses himself in the studies of magic and alchemy at a royal knight training school. However, following France's crushing defeat at Agincourt, the school is dissolved. Having lost everything and now a wanted man, Montmorency, who had just become an alchemist, encounters a mysterious village girl named Jehanne.
For 30 years, thousands have traveled to other worlds. The few that return keep the powers they had in those worlds. Akatsuki Ousawa returns from the world of Alayzard with the defeated Demon King's daughter, Miu. Miu pretends to be Akatsuki's sister to hide her true identity. They join Babel, a school for inter-dimensional travelers, and struggle against the student council to uncover the truth behind the school.
Akuma Kun, a boy raised by a demon, works with his half-human partner Mephisto III as paranormal investigators to solve various murder and mysteries.
