Tennis Boy is a ghost who haunts a tennis club.
He has beige short hair and purple eyes. He remained wearing his tennis uniform as a ghost.
Since the tennis club doesn't allow first-year club members to play on the tennis court, he spent one year picking up tennis balls. And even upon entering second year and getting the uniform, he remained stuck picking up balls (probably for not being skilled), and he passed away in an accident without ever playing on the court. As he longed to play tennis and spite those who play tennis regularly, his spirit remained plaguing the tennis club for years, by getting every tennis balls that would get out of the court and hiding them in a spirit road, which caused the tennis club to spend most of their budget buying new balls.
When the tennis club used up all their funds, Rinne was sought to solve the problem. After finding his spirit and learning his ties to the living world, he enlisted Sakura and Tsubasa to play a game of doubles with the spirit on the court, to help him pass on. However, the game took silly turns as he was not skilled and Tsubasa was competitive. But ultimately, he came to be satisfied by just practicing swinging with Sakura, and passed on, and all the stolen tennis balls return to the club.