IN Yuu Yuu Hakusho, in chapter black the main rival of Yusuke's is the former spirit detective Shinobu Sensui. His name Shinobu means hero. Which suits him perfectly because he was a hero when he was a spirit detective to the human side until he formed kazuya his other personality after seeing the sins of humanity . It is called chapter black because it's a video tape or rcodings of all of humanities sins. However, Shinobu forms up to 7 personalities each with their own traits and characterisitcs. He then switches over to form a tunnel leading into demon world so he can venture out into their land and experince what it would be like to be a stranger in a distant land. Hoping to stop him, the current spirit detective Yuske fights Shinobu and loses. But that pushes his friend's energy levels up to A class. however Shinobu's energy was sacred energy and that of S class so they couldn't even hurt him and then Yusuke had dormant Mazzakuy blood in him that was awoken because of a chain reaction. He then transformed killing Shinobu giving him catharsis at last. Ironically though, Shinobu only had a couple weeks left to live anyways before he died from some disease.