If you live in Japan and have hoped for a Ys VIII demo you can now download one on the PS Vita via The Playstation Store.
You can also save data from the demo and it will be compatible with the full version of the game. It will not, however, be compatible with DLC for the full version.
Ys VIII was originally released in Japan for PS Vita last month. The Playstation 4 version will be released next year.