Oh, make sure you don't miss the Aoi Boyfriend quest. It causes Aoi to leave the team and then rejoin. If you've done that, Michiko's quest should continue.
No i mean You should be in timeline 0 (real timeline). Michiko & Aoi are not bestfriends in timeline 2. Try asking Aya at Sunrays Apartment to switch your timeline to the real timeline. If that doesn't work either, i don't know if it's a bug or not.
