Orient unfolds in Hinomoto, where a peace that has lasted for 150 years hides a brutal truth. The samurai were driven from power long ago, and demons now rule the land after being worshipped as gods. Ordinary people are forced into labor so the demons can feed, while the reality of humanity's subjugation is kept hidden beneath obedience and ritual. Musashi has understood that lie since childhood, even as his anger and frustration push him away from his best friend, Kojirou Kanemaki.
That tension breaks on graduation day, when Musashi and the other new graduates are sent to the mines and see the cruelty of the system for themselves. The inhumane treatment of the miners and the disturbing appearance of their overseers confirm everything Musashi feared. With Kojirou's help, he survives a demon attack at the quarry long enough to witness a demon leader tear through the site and leave him on the brink of death, until the Takeda samurai clan intervenes and saves him. Humiliated but newly resolved, Musashi chooses the path of the samurai, determined to build his own clan and challenge demon rule for the future of Hinomoto. As the story widens beyond that first revolt, Musashi, Kojirou, and allies such as Tsugumi Hattori are drawn into larger battles between samurai bands and demon rule across the country.