HYAKKI CASTLE is finally on Steam now!
You can purchase this title on below link at a 20% discount for $19.99 USD during a limited time launch week sale.
http://store.steampowered.com/app/686740/HYAKKI_CASTLE/
An extra dungeon will be added sometime in 2017:
The additional dungeon features a high level of difficulty, and will be available in an update.Clearing this extra dungeon plays the full version of the biwa song, Dan no Ura, used in the trailer, and displays special end credits with information on Yokai appearing in the game.