Last mission (so I read) is kind of like an 80 floor chocobo dungeon. You can only use one girl at a time, and at every 20 floors there is a boss. And after the boss you get a little story. There are puzzles and enemies and bosses galore. And at the end a ship of some kind takes off for space I think (it's in Japanese so I'm just saying what it looks like is happening from screenshots).

It's too bad that we don't get it.