The latest installment in the 14 year-old franchise that is Kingdom Hearts follows a custom character as they learn to wield the keyblade. Taking place before the Keyblade War, it creates the optimal setting for an MMO type game, while still being incredibly important to the series. You can read more about how the game connects to the main continuity here. Kingdom Hearts Unchained:Chi at first glance may just seem like a game intended to hold us players over until December for Kingdom Hearts 2.8, but it is actually vital to the series, here's why.
There Are Heartless
This one is pretty obvious to anyone who has played the game, the primary enemy in this installment is heartless, not unversed, nightmares, or nobodies. While most people either don't notice it or just write it off, I think it means more. Most hardcore players remember that heartless were created by Ansem (fake Ansem, not Ansem the Wise) in the time between Birth By Sleep and Kingdom Hearts. This would make it seemingly impossible for them to appear before the Keyblade War, but as touched upon here, it could be possible for a few reasons.
Ever since the events of Kingdom Hearts: Dream Drop Distance we now know that time travel is in fact possible in the KH universe. With this knowledge, we can conclude that time travel had to be present somewhere in the timeline before Chi started, bringing heartless to Daybreak Town and beyond. Of course since time travel is apparently used here, we can only imagine there was a reason. While that is likely for one of the foretellers to be among the 13 Darknesses, it could also be a tell for the future of the series as well.
Following Kingdom Hearts 3
The game itself can be seen not only as a setup for Kingdom Hearts 3, but also as a setup for the series beyond. Chi primarily explores the lore of Kingdom Hearts, but it also provides an incredibly intriguing story. We are told that all but one of the foretellers are given information of traitor among them, obviously the traitor didn't receive that information. But with that knowledge, perhaps Xehanort brought the heartless to help provide a distraction while he takes the traitor foreteller to join the 13 Darknesses. But why does this matter to the series beyond Kingdom Hearts 3?
The Foreteller Becomes The Main Antagonist
Now this is where people may start to either see reason, or close the article. Assuming Kingdom Hearts 3 follows the typical good guy vs. bad guy model, Sora and pals should win, while Xehanort is defeated. The series is already confirmed to continue after 3, with Sora still as the main character, so who could take over the role of main villain? None other than the traitor foreteller. With that foreteller still around, perhaps after the failure of the 13 Darknesses, they wish to plunge the world into darkness by themselves.
Why It Works
Of course it would be on the crazier side, but if Kingdom Hearts has shown us anything, it's that it is crazier than we think. And what better time to release Kingdom Hearts Unchained:Chi in North America than a few months before KH 2.8 and just a year before KH3, if not for the sole reason to introduce players the the future antagonist?