Just as the Xbox One got a confirmed release date for Japan (due to be released Sept. 4), the Japanese Xbox site also updated its website with pages for many upcoming Xbox One games. One of those games is of course "Kingdom Hearts III":
Japanese Xbox KH3 Page
The page currently only has the announcement trailer from E3 2013, along with three images from the trailer, and the following description:
Credit to Zephyr from KHInsider for the translated description.
Japanese Xbox Site Launches KH3 Page