YuYu Hakusho, Vol. 1 by Yoshihiro Togashi

[Viz] A delinquent’s gotta do what he’s gotta do…in the afterlife. Yusuke Urameshi was a tough teen delinquent until one selfless act changed his life...by ending it. When he died saving a little kid from a speeding car, the afterlife didn't know what to do with him, so it gave him a second chance at life. Now, Yusuke is a ghost with a mission, performing good deeds at the behest of Botan, the ferrywoman of the River Styx, and Koenma, the pacifier-sucking judge of the dead. Yusuke Urameshi was a tough teen delinquent until one selfless act changed his life...by ending it. When he died saving a little kid from a speeding car, the afterlife didn't know what to do with him, so it gave him a second chance at life. Now, Yusuke is a ghost with a mission, performing good deeds at the beshest of Botan, the spirit guide of the dead, and Koenma, her pacifier-sucking boss from the "other side." But what strange things await him on the borderline between life and death?