ONA
Description
Imperial Prince Atsumi is a supporting character in the anime Onmyōji. He is the eighth prince of Emperor Uda, who ruled two generations before the events of the story, and he holds the reputation of being the greatest court musician in the capital. A patron of the arts, he is especially celebrated for his mastery of the flute, and his standing among the nobility is high. Within the story he also serves as the flute instructor to Minamoto Hiromasa, and he is a naturally anxious guardian figure who frequently worries about Hiromasa's safety, particularly when the young noble becomes involved with the onmyōji Abe no Seimei and the dangerous supernatural affairs that surround him. In appearance, Atsumi is depicted as a dignified man with black hair and green eyes, and his bearing reflects his courtly upbringing. His background loosely mirrors that of the historical figure of the same name, a real eighth son of Emperor Uda remembered for his contributions to court music, though the anime develops his character in its own direction.

Atsumi's personality is outwardly composed and refined, consistent with his position as a respected senior member of the court. Beneath that composed surface, however, lies a more vulnerable sense of pride. He was the one who taught Hiromasa to play the flute and helped nurture his talent, but over time Hiromasa's natural ability came to exceed his own. Hiromasa even obtained a magical flute that could only be played by a musician of genuine skill, a development that made Atsumi's feelings of being surpassed impossible to ignore. Atsumi kept his jealousy hidden, but the resentment festered, and a demon eventually took advantage of these emotions, manipulating him into merging with it. The transformation turned Atsumi into a demon himself and brought his suppressed envy to the surface as outright hostility toward Hiromasa.

His role in the narrative begins as that of a mentor and background figure, but it becomes significant in the final arc, when the demon-possessed Atsumi emerges as a threat. In the climax, after Seimei brings Hiromasa back from death through a risky ritual, the demonic Atsumi attempts to kill Hiromasa. Rather than meeting violence with violence, Hiromasa approaches him with affection and forgiveness and cuts away the horns that mark his demonic form, an act that restores Atsumi to his human self.

Atsumi's development is therefore an arc of fall and redemption. His jealousy, though long suppressed, leads him to become the kind of demon that the story's protagonists usually oppose, but his bond with Hiromasa proves strong enough to save him. After returning to his human form, he cannot simply resume his old life, because members of the court saw him in his demonic state. He chooses instead to withdraw from the capital and set out on a solitary journey, keeping his whereabouts unknown. Even Seimei regards this decision as sensible, since it protects Atsumi from the gossip of the court.

In terms of abilities, Atsumi's distinction lies in his artistry rather than in magical practice. His flute playing is his defining talent and the source of his fame, and the only supernatural power he demonstrates comes from his demonic transformation, which grants him demonic strength and appearance, including a pair of horns. After his redemption, he loses this demonic power and returns to being an ordinary, if exceptionally skilled, musician.