Kingdom Hearts III is the best-selling console game in the Kingdom Hearts series. The 2019 title has outsold every other game in the series, and it's brought the series to unprecedented pop culture heights. That sounds like a good thing for Square Enix and for the series as a whole, but it will probably result in more harm than good for the Kingdom Hearts brand.
Kingdom Hearts is a little bit of a mess. The story is wildly convoluted, with nearly every seemingly insignificant plot point and character ultimately holding some piece of the massive puzzle. The culmination of that massive mystery, the moment in which every single piece falls into place to deliver one semi-coherent thesis, is Kingdom Hearts III. The fact that it is the best-selling title in the series means Kingdom Hearts III was the first exposure many fans had to the world of Kingdom Hearts. That cannot possibly have been a pleasant experience.
Kingdom Hearts III does absolutely nothing to onboard new fans. It picks up right where Kingdom Hearts 3D: Dream Drop Distance, the 3DS spinoff, ended, with a handful of interruptions from flashbacks featuring characters from Kingdom Hearts: Birth by Sleep, the PSP prequel. None of these characters or events are introduced at all. The game is presented with the assumption that the player already knows what's happening. After all, they've played the previous games. Of course, many players haven't played those previous games, and came to Kingdom Hearts III expecting a standalone experience.
The meteoric success of Kingdom Hearts III certainly isn't upsetting to Square Enix. In the short term, after all, the studio makes lots of money off of high sales. In the long term, though, the most complex and convoluted entry in a series that's already difficult to comprehend cannot be the entry point for new fans. If members of a series' audience associate that series with confusion, they aren't going to want to return for the next title.
Kingdom Hearts IV is officially in development, and a trailer has been shown for the game. Kingdom Hearts III was billed as the end of the "Dark Seeker Saga," and many fans might assume that Kingdom Hearts IV will act as a new and approachable way to get onboard with the series. Unfortunately, those fans are wrong. Kingdom Hearts IV will almost certainly be as grounded in extraneous materials as its predecessor.
In the one trailer released for the game so far, there's already been footage of Strelitzia, a character introduced in the online mobile game Kingdom Hearts Union χ. That game went offline in 2020, and its app now holds a cutscene library which is not arranged in chronological order, meaning fans who want to understand what's happening in Kingdom Hearts IV will likely need to download a defunct mobile game and find a fan-made list of the cutscenes just to experience a subpar version of an already bizarre story.
Additionally, Kingdom Hearts IV seems to be incorporating elements of the rhythm game Kingdom Hearts: Melody of Memory, as well as the Re:Mind DLC for Kingdom Hearts 3. The game is also the beginning of the "Lost Master Saga," almost certainly a reference to the Master of Masters, a character who appeared first in Union χ and was better developed in Kingdom Hearts χ Back Cover, an animated movie included in the Kingdom Hearts HD 2.8 Final Chapter Prologue compilation.
Beyong that, director Tetsuya Nomura says the upcoming mobile game Kingdom Hearts: Missing-Link and the recently-completed Kingdom Hearts: Dark Road will both present important lead-ins to Kingdom Hearts IV. It's not getting any easier for newcomers to understand Kingdom Hearts. In fact, it's only getting harder.
Kingdom Hearts has backed itself into a corner. The story has become so massive that dedicated fans who have devoted hundreds of hours to its world will be disappointed in any experience that doesn't reward their enthusiasm, while the wave of newcomers who joined the fray with Kingdom Hearts III will be unlikely to even want to stay on the ride for Kingdom Hearts IV, especially if it doesn't make an effort to initiate players into its wildly convoluted world. For some, the twists and turns of the Kingdom Hearts series are part of the appeal. For many, though, they represent a barrier that prevented them from enjoying Kingdom Hearts III, and will likely continue to prevent them from enjoying the series in the future.