I went to the Bravely Default: Flying Fairy site to download the AR marker for Tiz’s story and noticed Square Enix updated the credits. The site reveals Naotaka Hayashi, the scenario writer on Steins;Gate and Chaos;Head, wrote the story for Bravely Default: Flying Fairy. I believe this is Square Enix’s first time working with 5pb Games/Mages too.
The demo should be available on the eShop soon. Grab the AR marker if you have a Japanese 3DS or one of the desktop accessories (click on the black Bravely Default logo) here.