Character Arc
The Medicine Seller, known in Japanese as the Kusuriuri, is the enigmatic protagonist and the only character to appear in every arc of Mononoke. A wandering merchant with pale skin, elaborate robes, and a fixed, knowing smile, he arrives wherever a mononoke has taken root and calmly sets about confronting it. He is less an action hero than an investigator and a kind of exorcist, and much of his appeal lies in his unflappable poise in the face of the uncanny.
His method gives the series its shape. He carries a sealed sword that can banish a mononoke, but it can only be drawn once he has identified the spirit's Form, its Truth, and its Reason, that is, what it is, what really happened, and why the emotion behind it lingers. Pursuing those three answers forces him, and the audience, to reconstruct the concealed human tragedy at the heart of each story, so his presence drives both the supernatural and the mystery elements of the show.
The character is deliberately mysterious. His true name, origins, and nature are never spelled out, and a striking second aspect emerges only when he draws the sword. This restraint keeps him compelling across the anthology and made him an icon of the series, carried over from his debut in the Bakeneko segment of Ayakashi: Japanese Classic Horror into Mononoke and later revivals of the property.