Ghost!

Mitsuo Shiozu is a lonely high school student who happens to be psychic. Spirits 'use' his body and mind to communicate with the dead and to help the living. These ghostly apparitions use Mitsuo in order to put right things that were left undone in life, or to tie up ends that were left loose before they left the land of the living.
In the process, Mitsuo often finds that these 'visitations' change his own life in ways he could not predict.
(Source: Tokyopop)