The latest issue of Famitsu Magazine contains a few Kingdom Hearts Unchained X scans! The scans mentions various features previously announced such as customization, keyblade rankings, the medal system, quests, etc. For a more detailed summary, view below. Kingdom Hearts Unchained X is set to release in September 2015 in Japan. Release Dates for other countries are currently unavailable.
Kingdom Hearts Unchained X Famitsu Scans Summary
The setting takes place prior to the Keyblade Wars
Create your avatar
Choose a Union (in-game faction)
Daybreak Town will be the hub world (join parties, visit shops, check rankings, keyblade customizations, etc)
Avatar Board Messaging System (exchange Avatar coins for costumes and abilities, message and stamp members in your party)
Medals have rarities, attributes, cost, ability, default skills and statuses
Upgrade medals through synthesis which could increase rarity and change appearance
Quest material can upgrade a Keyblade
Raid Bosses appear during quests
Thanks RedMakuzawa for the scans!