WARNING: The following contains major spoilers for Kingdom Hearts III, and the series as a whole.
Secret endings have been a part of the Kingdom Hearts franchise from the very beginning; upon fully completing the first game, players were treated to a teaser for Kingdom Hearts II, which itself had a secret trailer for Birth By Sleep.
Despite some believing that Sora's adventure, and even the story of the franchise as a whole were coming to a close with Kingdom Hearts III, the game continued the trend of unlockable cutscenes, including a secret ending that could be a preview of more to come. Even diehard fans have been having trouble figuring this cutscene, as well as the main ending and epilogue, so we thought we'd take a crack at it, showing you how to unlock the secret ending along the way.
Let's start with the main ending and the epilogue that follows. After Kairi is straight up Keyblade-murdered by Xehanort (who turned into his younger, innocent self at the end of the battle, so we guess he's forgiven?), Sora is determined to bring her back. The logistics of this are a bit hazy, but we know for a fact that Sora succeeds in his mission, as the final cutscene ends with Kairi returning to Destiny Islands, sitting hand in hand with Sora.
Unfortunately, only seconds later, Sora fades away into the sunset in the scene's final moments, leaving players both devastated and confused. Though we don't have an exact, detailed answer for you (no one can begin to comprehend the mind of Tetsuya Nomura) the basic takeaway is that Sora, in some way, sacrificed himself to save Kairi, perhaps giving up his heart once again to save her from the darkness. Kairi obviously knew as much, since she sheds a knowing tear before Sora fades away.
Additionally, the game features a post-credits epilogue (not to be confused with the secret ending) which reveals that Organization XIII member Xigbar was actually Luxu, one of the apprentices that sparked the Keyblade War early in the lore of Kingdom Hearts. It's also revealed that he was in possession of the Black Box Maleficent and Pete were searching for, a plot point that was noticeably missing from the rest of the game. That it's brought up here shows there are clearly storylines that have yet to be wrapped up, giving fans hope for at least one more chapter.
Unlocking the Secret Ending
One might be tempted to join Kairi in shedding a tear for Sora fading away from existence, but hold onto those feels, folks, because there's more to the character's story. In order to see more of Sora, and perhaps learn what has become of him, players must unlock the game's secret ending, which is significantly easier than it was in previous games. Where Kingdom Hearts and Kingdom Hearts II forced you to complete the game in its entirety -- including perfect mini-game scores, finding all treasures and defeating secret bosses -- Kingdom Hearts III is a lot less difficult.
In order to unlock the game's secret ending, all you have to do is find and take pictures of every one of the Lucky Emblems, the game's version of Disney parks' notorious hidden Mickeys. The amount of Lucky Emblems (which range from imprints on walls, to round objects forming a Mickey shape) needed to get the secret ending are different for each difficulty setting. If you choose Beginner Mode, you'll need to find 90 emblems, if you choose Normal Mode, it's 60, and if you're one of the brave souls who chooses Proud Mode, you'll only need to find 30 Lucky Emblems.