How to get King and Master:
First to get King you have to beat all normal matches and all training games in world circuit to unlock a level 4 match against King. After you beat him you'll unlock a doubles match against King and Master. After you beat that final match you'll get King to use in arcade and exhibition matches. To get Master you must play arcade mode on very hard (might be able to get on normal also not sure I only play very hard) and win every single game and set straight through, you cannot lose any games or matches if you do it will not work. After you beat the last guy you'll see your character celebrate and then it will say new challenger, it will be Master. Beat him and you'll now be able to use Master in arcade and exhibition modes. To make this easier you can put the amount of games on 1 the number doesn't make a difference on the amount of money you get or affect facing Master after the last guy.

Here are a few pointers on Master first he doesn't have 150mph serves like King but he'll throw you some tricky serves that go slower then they look just be ready to move up on them and swing do that and you'll have really no problem beating him hes not really harder then most of the other characters as long as you don't make bad shots which he'll burn you on, as for King the only real problem with him is the 150mph serves you just have to be real fast and judge it very good and move up on it at the right time other then that hes easier then Master to beat.

Play against Master and King
Successfully complete arcade mode using no continues and without losing a round on the normal difficulty setting to play against Master in singles and Master and King in doubles. This can be easily done if the match is set to one round.

Play as Master
Defeat Master in singles in arcade mode to unlock him in arcade and training modes.

Play as King
Successfully complete all 22 trial and 24 training levels in world circuit mode to reach the number one ranking and have King challenge your player. Defeat King to unlock him in arcade and training modes.

Underarm serve
To do an underarm serve, press A + X + Down while at near court, or A + X + Up while at far court.

Sunflower costume
Successfully complete the big wall training level with at least ten seconds left on the timer to unlock costume no. 22.

Tambourine costume
Successfully complete the bull's-eye training level with a score of at least 7000 to unlock costume no. 23.

Camouflage costume
Successfully complete the cannon training level before the timer turns red to unlock costume no. 24.