Kohaku is Sango's younger brother. He was a nice little boy that was trained to kill demons, his first job cost him his life and all the ones around him. An evil spider demon controled him and caused him to kill the demon slayers around and almost kill his sister. He came to when he hit his sister in the back with his nasty weapon. He was then shot down with arrows and killed with his sister on top of him. He was later brought back to life by Naraku  thanks to a shikon jewel inbeded in his back. Naraku uses him against Inuaysha and his gang because they won't kill Sango's brother.

 

Hook on a Chain-His weapon is a giant hook that is on a chain. He can throw it and retrieve it. It may seem like nothing, but he has killed whole villages with it.