When you beat the final boss, there's hinted at more story progression in the scene after the boss. But me and several other people were discussing it and none of us have actually found anything following the given clues.
The guy that gave you assignments runs off with the reincarnation book and one of your party members hints at chapter 2 and chapter 8 to investigate where he went. But there's no maidens or Itako anywhere, not even when entering NG+.
So maybe an official can answer this?