Gematsu reports that the battle demo will be available in Japan on August 12. The demo will allow for multiplayer (up to four players) ad-hoc play. It will feature one Gigantes to be battled, named “Agrios”, and will also feature cutscenes for limited insight into the characters alongside limited exploration of the planet Machia as we’ve written about before. The size will be one gigabyte – be sure to have a sizable memory card!
Update (August 6, 2014): Siliconera writes that character creation and story progression are not features available to the demo. A helpful note for anyone wondering!