Yoshi Nakamura is the custodian of Seaford High School as seen in "Fat Chance". He saved Milton from falling over and Milton sees him as his guardian angel. He used to be the sumo wrestling champion and even has a victory dance called The Nakamura Stomp. He retired from Sumo Wrestling when a rookie named Yamazaki beat him in a sumo match but with the help of Milton and the Wasabi Warriors he was able to get back in sumo wrestling and go to Japan and retire from his custodian job. It is also mentioned he went to a game show called Are you willing to lose all your life savings and lost all of his life savings.
Info was provided http://disneyskickinit.wikia.com/wiki/Yoshi_Nakamura