Summary
With 2024 rolling in, fans are one step closer to unwrapping the mystery that isKingdom Hearts 4. Currently existing as little more than a teaser trailer, the latestKingdom Heartsproject from Square Enix and Disney promises to be another fun romp through their unique crossover universe. Series protagonist Sora will have to find his way out of the enigmatic otherworld known as Quadratum, with plenty of intrigue building up in the background. As the Dark Seeker Saga ended withKingdom Hearts 3andMelody of Memory,Kingdom Hearts 4will begin the Lost Master Arc.
This new arc should cover plenty of new ground for the series, even if it also spends a lot of time addressing old story threads.KH3promised the return of the Foretellers and presumably the Master of Masters fromKingdom Hearts χ, while also leaving several plot threads like Subject X and the Nameless Star unresolved. Even the supposedly deceased Strelitzia has returned fromKingdom Hearts Union Crossto take Sora’s side. However, in the face of all these new mystery elements,Kingdom Hearts' traditions also shouldn’t be forgotten inKH4, least of all the object that gave the series its name.

What Does The Title of “Kingdom Hearts” Refer To?
Despite being integral to several games’ stories, details about the in-universe Kingdom Hearts still elude fans. Since the first game, Kingdom Hearts has consistently been the target of Xehanort’s schemes to destroy the Realm of Light with a flood of darkness. Serving as the heart of all worlds, and potentially the first source of light and life if Xehanort is to be believed,Kingdom Hearts is normally hidden within the Realm of Darkness. It takes the formation of the χ-blade to summon and control it, although the Door to Darkness inKH1presumably allows physical access, and Organization 13 built an artificial Kingdom Hearts out of mortal hearts inKH2.
Xehanort’s ambitions to corrupt it with darkness and remake all worlds have been foiled, but future villains will continue to pursue Kingdom Hearts for their own ends. However, there’s no telling when or how Kingdom Hearts will appear next.Kingdom Hearts 4’s displaced setting of Quadratummay not interact with Kingdom Hearts in any established way, and the intentions of the potentially-villainous Foretellers and Master of Masters for it haven’t been seen either. The Lost Master Arc could do almost anything with Kingdom Hearts, but there might already be a plan for it in motion.

Why Kingdom Hearts Probably Has A Big Role To Play in KH4
The biggest hint about Kingdom Hearts’ presence inKingdom Hearts 4’s Quadratum actually lies in theunlockable ending ofKingdom Hearts 3. A hooded figure, commonly believed to be the Master of Masters, is seen forming their hands into a heart to frame Quadratum’s moon. Kingdom Hearts’ true shape is that of a heart-shaped moon, so this could be interpreted as the Master of Masters’ intent to summon Kingdom Hearts in Quadratum.
There Are Multiple Ways For Kingdom Hearts to Manifest In The Lost Master Arc
TheKingdom Hearts 4teaser implies that Sora is still able to travel to other worlds from Quadratum, raising the question if Quadratum’s unreality has its own heart of all worlds. It could be drawn out by Sora’s presence sparking a conflict between light and darkness, orthe villains ofKH4’s Lost Master Arccould harvest hearts from Quadratum’s urban population to build another false Kingdom Hearts. The Master of Masters wishes to destroy all darkness at any cost, so Kingdom Hearts could be used to wipe away existence with a flood of light instead of Xehanort’s darkness. Regardless of how it appears, Kingdom Hearts has yet to skip a numbered entry in its series, so players should expect to see it again inKingdom Hearts 4.