I'm not sure if the ending is meant to be ironic, but I think the series sets a new standard when you've a sports manga that can do stuff not even Goku can do. Apparently Yukimura's assertion that "There is only one tennis ball" is actually a lie. There are actually TWO tennis balls. Ryoma, after going his super saiyan limit 3, hits the ball hard enough that it physically breaks into 2 in midair and overwhelms Yukimura for the win. Note that while plenty of people can create illusions of ball (up to about 15 has been observed), they are still just illusions. Now obviously Goku can smash a tennis ball in half, but I'm quite certain if you break the ball in half then the point gets stopped, and assuming Goku is interested in playing by the rules of the game, this is something he cannot do.
Up until this point, only Fuji's double spin hit would be something that is considered illegal (he hits with a top spin and then flips his racket around and hit it with a back spin, thus hitting the ball twice). It's really bad when you don't even go by the rules of the game. It'd be like making a 5 point shot in a basketball game. This might be why Prince of Tennis was axed halfway and none of the loose ends were even closed to being wrapped up, not that there was any depth to the story.
Up until this point, only Fuji's double spin hit would be something that is considered illegal (he hits with a top spin and then flips his racket around and hit it with a back spin, thus hitting the ball twice). It's really bad when you don't even go by the rules of the game. It'd be like making a 5 point shot in a basketball game. This might be why Prince of Tennis was axed halfway and none of the loose ends were even closed to being wrapped up, not that there was any depth to the story.
