After you defeated the Jade Oni, did you give the emperor the healing potion? If so, he should have sent you to see MA and he would have sent you to see Drake. Drake requires you to battle him to see if you are ready for DS. Once you beat Drake, you are off to DS.
Hi, I too was stuck in Mooshu after my first Jade Oni fight. The quest would only partly update. After summoning the Jade Oni from the braiser and besting it again was I able to get the Emperor to give me permission to talk to the Head Master. I guess sometimes you must retrace your steps and refight some fights. If that does not work email tech support.
I think you have to be in the 1st position when you defeat the Jade Oni inorder to get the potion for the emporer. My sister and I fought ther Jade Oni I got the potion she didn't after 2 more attempts I had her go first and she completed the quest.
During my first fight with the Jade Oni I was solo. I was still able to solo him though. During that fight I forgot my Legends Shields and had to use several more heals and two pets . My computer briefly lost connection with the server during the fight. I did win it though. With the shields it is much easier. How many potion bottles are you supposed to have after mooshu? I only have three.