The Eastern Kingdom of Mikado is a relatively tranquil kingdom, where the affluent Luxurors and poor Casualries exist within a caste system. Maintaining peace and defending its citizens from the demon threat is the samurai class, composed of individuals from both Luxuror and Casualry backgrounds.

One such samurai is a young Luxuror-born boy named Jonathan. From a young age, Jonathan has always dreamed of joining the order in hopes of being able to protect and serve his empire. Training beside him every day is Asuma, a young Casualry orphan. Driven by the death of his parents at the hands of demons, Asuma strives to become a samurai and eradicate them from their world. After a demonic incident occurs during one of their sparring sessions, Jonathan and Asuma are separated from each other until the day of the samurai prentice exam, 10 years later. The time apart has created a rift between the two former friends and causes them to no longer see eye-to-eye.

Shortly after the exam, the two boys are appalled to learn that samurai must utilize demons in order to effectively defend the people of the kingdom. While Asuma vehemently refuses to make any deal with the enemy, Jonathan's devotion to his beliefs wavers as he forms an unlikely partnership with a demon named Al. As the threat of illegal "literature" grows amongst the Casualry class and turning those who read it into demons, whose conviction will ultimately prevail?

[Written by MAL Rewrite]