Suikotsu is a minor character from Inuyasha and is a member of the Shichinintai who suffers from Multiple Personality Disorder. He has two, definite sides of him: a peaceful doctor who cares deeply for children, but has a fear of blood, while the other is a bloodthristy murderer with a penchant for slaughter.
In the Story
He starts showing his first signs of multiple personality disorder about a decade before the events of the story, when his village is destroyed by soldiers and its inhabitants are slaughtered out of cold blood. He avenges his village by killing the soldier, and due to the fact that he had never done such a thing in the past, his personality splits into two. Soon after, he joins the Band of Seven.
Following his resurrection, he finds work as a doctor in a village near Mt. Hakurei. The holy aura permeating the surrounding area keeps his evil side in check, and he becomes popular with the children of the village. He fears the sight of blood, which seems to awaken his evil side even when close to Mt. Hakurei.
In both the anime and manga, Suikotsu died after a battle with Kikyō and Sesshōmaru, the latter of which decided to fight him after he kidnapped and threatened to kill Rin. After suffering a fatal attack from Kikyo's arrow strike and regaining his good persona, he asks Kikyō to remove his jewel shard from his neck so that he can return to bones. Kikyo asked that Suikotsu wishes to choose death. Suitkotsu says he now remembers everything he had done and to prevent his evil persona ever taking over his consciousness he begs Kikyo to kill him. Sadly however, Jakotsu violently removes the shard instead and Suikotsu returned to his skeletal state. The good but unfortunate doctor finally found his peace in death.