"Orient" is set in an alternate version of feudal Japan where demons, known as Oni, have overrun the land, forcing humanity into subjugation. The story begins in the Awaji Island region, where Musashi, a young boy, dreams of becoming a powerful warrior to fight the Oni and liberate humanity. However, society has been manipulated into believing that the Oni are divine beings, and those who oppose them are branded as heretics. Musashi, along with his childhood friend Kojiro, secretly trains in the forbidden art of bushidō, the way of the warrior, despite the societal taboo.

As the narrative progresses, Musashi and Kojiro encounter a group of rebels known as the Bushi, who wield mystical weapons called Obsidian Swords to combat the Oni. These weapons are imbued with the power of the Kishin, ancient spirits that grant their wielders extraordinary abilities. Musashi awakens his own Kishin, a powerful entity named Shirō, which marks him as a key figure in the fight against the Oni. Together with Kojiro, who also awakens his Kishin, the two join the Bushi and embark on a journey to unite humanity and challenge the Oni's dominion.

The series explores themes of rebellion, camaraderie, and the struggle for freedom as Musashi and his allies confront both the Oni and the corrupt human factions that collaborate with them. The story delves into the complexities of power, loyalty, and the moral ambiguities of war, as the characters navigate a world where the lines between hero and villain are often blurred. Musashi's growth as a leader and warrior is central to the narrative, as he learns to harness his abilities and inspire others to rise against oppression.

Key characters include Musashi, the determined and idealistic protagonist; Kojiro, his pragmatic and fiercely loyal friend; and Naotora, a skilled Bushi who becomes a mentor figure to the duo. The Oni are depicted as formidable adversaries, with their own hierarchy and motivations, adding depth to the conflict. The series balances action-packed battles with moments of introspection, as the characters grapple with their roles in the larger struggle for humanity's survival. Through its exploration of a richly imagined world and its focus on the bonds between its characters, "Orient" presents a compelling tale of resistance and hope in the face of overwhelming odds.