Taoist Yu was not the fellow male junior apprentice of Old Man Mu, but had a relationship with the Yuqing Sect, which came from the Central Plain. Old Man Mu had found out about it recently.
When talking about the relationship between the Central Plain and Norland, people only mentioned it vaguely. They either were ashamed to talk about it or only knew a little about it, because it had happened 70 or 80 years ago.
The result of the split was obvious. The Norland took away a lot of external-style kung fu, while the Central Plain possessed all Internal Strength. Neither side benefited, but rather lost their good reputations gradually and became unremarkable sects.
Old Man Mu was the only disciple of Norland left today, but he brought new hope to the Yuqing Sect.