Hikaru no Go, Kurogane Recommendations
A ghost/shinigami appears to the heroes as teachers and then the boys want to become better in the game/sport. They both have explanations too so readers don't get confused.
Both have earth bound spirits that cannot rest due to their strong attachments to their respective sport/game. H no Go is more serious while Kurogane has a very strong element of humour. Both are enjoyable reads, although Kurogane has only recently started serialization. Oh, and watch out if you don't like prolonged explinations of various moves and tactics (especially for h no go).