During a Tokyo Game Show
Below is a video taken from the livestream, captured by News Team member Jake. The official trailer will be added as soon as it is available.
A translation of Chirithy's dialogue can also be found below, thanks to News Team member soraspromise.
This is where our story began. Based on the prophecy, the five disciples undertook missions from their master’s teachings and formed their own unions. After Heartless began to appear, they began to collect Keyblade wielders who shared their mindsets and asked them to collect the “light”.
This same dialogue can be found in the issue of Famitsu Weekly that released on September 17th, used as a description for Kingdom Hearts χ Back Cover which was announced to be a part of Kingdom Hearts HD 2.8 Final Chapter Prologue at SCEJA's 2015 press conference.