Yu

History
Even though Master Yu is treated with a great deal of respect, he doesn't seem to be the powerful Earthbender that everyone treats him as. Although, he may simply be holding his real skills and knowledge back from his students so that he doesn't have to strain himself teaching them as he is shown keeping up with Xin Fu in "The Desert,". When receiving a free lesson, Aang is quickly beaten by a younger student, and Master Yu suggests that Aang pay for a year of lessons and that if he pays in advance, he'll bump him up to the next belt. This suggests that he is more a businessman than true master, as this is a common practice among less-than-reputable martial arts schools in America. He's now working alongside Xin Fu to retrieve Toph, whose father incorrectly accused Aang of kidnapping her. Offering them a bounty for her return, united by a "mutual interest" they accepted.

In "The Desert," they reach Misty Palm Oasis at the edge of the Si Wong Desert on the trail of the Avatar and Toph. Master Yu appears to be the more level headed of the two; he reminds Xin Fu (whom mistook the bounty as dead or alive) that Lao Bei Fong wants Toph alive. Xin Fu temporarily changes their target to the fugitives Zuko and Iroh to collect more bounty. Ignoring Master Yu's advice, Xin Fu directly confronts the fugitives but the White Lotus member turned all the desperate men in the bar against them. Although outnumbered Master Yu and Xin Fu dealt with them easily with their impressive Earthbending skills, but in the confusion the fugitives escaped. They searched the whole town but to no avail, finally going back to tracking Toph and the Avatar. They succeeded in capturing Toph at the end of "The Earth King", luring her into a trap with a forged letter from her mother. In "The Guru", Master Yu is captured by Toph in the very metal box he imprisoned her in.

Trivia

 * Master Yu appears in "The Blind Bandit", "The Desert", "The Earth King", and "The Guru." According to the leaflet from his school in The Blind Bandit, Master Yu's name is written as 余師傅 (yúshīfù). Yú (余) is a chinese surname and 師傅 (shīfù) means 'master' which as a title is put end of a teacher's name.


 * Master Yu and his academy serve as a satirical parody of atypical "strip mall" dojos where parents are able to purchase belts for their children in disregard of the symbolism and substance behind them, as well as a reflection of Sifu Kisu's and Bryan Konietzko's own personal disdain for the use of belt systems.