Hikaru no Go, Ginban Kaleidoscope Recommendations
Both deal with ghosts who help the main character improve in their sport.
Both main characters are possessed by ghosts and take time to get used to the situation. They also get advice from the ghosts that helps them (attempt to) accomplish their goals. And who could forget the fated departure of the ghosts into heaven, which is quite emotional in both series.
Both main characters get posessed by a dead person / ghost. At first they don't like it too much, but as the story continues they build up a deep relationship with the ghost.