Question about Mu in tiptop, thx!

[gaoyutailang]

at first, I fought Mu in Reemu's place for quest. Later, I want to fight mu and vischief again for armors, however, I　couldn't go back to town after the fight with Mu in tiptop. and in reemu's place, I only see vischief alone. I'm not sure if this is a bug or not, Could you tell me how you guys fight mu over and over again with returning back to town at final?
thank you so much