I suddenly thought of something...
You know how there was a scene after the rugby match where
Jay comes home to find his dad playing the piano...
Jay says: You seem to play pretty well when I am not at home
Then, his dad answers, "I only just learnt this"
He wouldn't reply who taught him when Jay inquired.
Thinking about it, at that point in time 20 years ago,
Jay's dad would have helped Xiao Yu out with her problems,
could it have been Xiao Yu who taught him to play??
Just a theory though
Humans are destroyers of the worlds.
Humans shall destroy them selves in the end.