Yu Yu Hakusho is the story of 14-year old Yuusuke Urameshi, a juvenile delinquent who spends his time wagging school and being a legend at street fighting. One day, while Yuusuke was wagging school as usual, he saves a child from being hit by a speeding car, and was killed.But wait! All is not lost! After his death, Yuusuke meets Botan, a denizen from another world who says that there is no room in heaven or hell for him, as his death was totally unplanned and it was not his time to die yet.
Yuusuke laughs at this, saying that he had died in place of the child, so why isn't there be a place for him? Botan answers by telling him that even though the child was meant to be hit by the car,he would not not hurt in any serious way, and didn't die. So Yuusuke had dived in front of the car and killed himself for no reason at all. Since there was no room and this was an unusal case they gave him another chance at life.
Yuusuke was then taken to Reikai (the name for the other world) to see the "person" in charge, called Koenma for a test, which he passed and hence was reincarnated as a psychic detective for the Reikai to catch criminals from Makai (the demonic plane) and monsters who had sneaked into the Ningenkai (the place where humans lived). The test was actually a test of his virtues; it involved him carrying the egg of a ReikaiJyuu; an animal of Reikai. This ReikaiJyuu lives on the energy Yuusuke emits; if Yuusuke is kind-hearted, the the ReikaiJyuu will become an angel, but if Yuusuke is evil, the ReikaiJyuu will become a monster and eat him when it hatches. Yuusuke gives up the egg when Keiko is trapped in a fire, and because of this act he was reincarnated. The egg business vanishes for a while, but resurfaces when the egg hatches to reveal Yuusuke's likeness in mind; a blue penguin-like bird they dubbed Puu. As low as it render's Yuusuke's intelligence, this bird actually morphs into a cool-looking phoenix when Yuusuke undergoes transformation into a youkai.
As Yuusuke's powers increase, so does that of his enemies. He builds up a team of friends, some of which are demons themselves, and gets involved in demonic fighting tournaments, Makai and rifts between worlds. Yuusuke's party generally became known to include four people. One of them is his eternal enemy/friend, Kazuma Kuwabara who too is a juvenile delinquent but has psychic talents. The other two are demons, or one-and-a-half demons, in which Yuusuke apprehended in his first assignment. They are the famous robber of today's Makai, Hiei, and the famous robber of yesteryear's Makai, Kurama.