There's a very short teaser for the next game, Cell of Mirage, called Interlude. It doesn't require any save files and doesn't require Locale Emulator, but if you start it before you've played all the rest of the series you'll be confused.
iseekyou.itch.io/cell-of-empi...

Cell of Empireo has a followup, shorter game, unlocked with a save file from the true ending of the base game. It's called Records of Sanemitsu Isoi.

iseekyou.itch.io/records-of-s...
Again, please remember to read the download page: you can't play the DLC without a save file.