To unlock the Umpires below win the following match.

Umpire	How to unlock
Anna	Beat Big Chief (Rock Bull) and Kent (aka Ryu) in World Class.
Kaori	Beat Kaito and Momoko in Semi-pro Class.
Robot Tennis	Beat Suzuki and Big Chief (aka Rock Bull) in Pro class.
Suzuki	Beat Cody (aka Yuki) in Beginners Class.