Although no sign of it has emerged since its 2022 reveal, Kingdom Hearts 4 continues marching toward its inevitable release. Hearing something about it before 2025 passes is possible, especially if Kingdom Hearts: Missing Link accompanies it, but all that can be done for now is more waiting and theory formulating. Kingdom Hearts 3 and its ReMind DLC concluded the series’ Dark Seeker Saga, and Kingdom Hearts 4 will officially mark the Lost Master Arc’s start, so fans have plenty of old information and lingering questions to mull over in the meantime.
Not only will the Lost Master Arc mark the first major narrative transition in Kingdom Hearts, it will also take a large step towards the series’ end. It’s too soon to say if Sora and company’s final battle will take place in the unreality of Quadratum or across time and space like Xehanort’s final showdown in KH3, but a mixture of old and new major players will need to start moving into place for the finale. Sora and KH Union Cross’s Strelitzia have been confirmed as two of KH4’s returning heroes, but there should be more familiar faces dropping in as the game moves on.

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Kingdom Hearts 4’s Quadratum is certain to feature newer faces like Yozora, but several characters from the past could appear again as well.
Donald and Goofy
The first teaser trailer for Kingdom Hearts 4 only contained two other characters of substance, and those would be Donald and Goofy. By the looks of things, they appear to be paying Hades a visit to ask about something, potentially Quadratum’s existence as an alternate afterlife. Per Kingdom Hearts tradition, other series regulars like King Mickey, Yen Sid, and Kairi will probably appear in cutaway cutscenes across KH4, but Sora’s oldest party members have the best shot at actually dropping in on the action. Even though Kingdom Hearts 4 could develop a new party, the classics can’t be beat.
Riku
Sora’s oldest friend is a close runner-up, however, and Riku has a good shot at appearing in Kingdom Hearts 4. Kingdom Hearts: Melody of Memory ends with Riku using the Power of Waking in the Final World to try and reach Sora, and odds are he’ll succeed sooner or later. Like Donald and Goofy, Riku’s appearance in Kingdom Hearts’ future is basically a given, and the bigger question is how much of the spotlight he’ll have to share with any newcomers. Kairi should also return to complete the Destiny Island trio, but she and the Wayfinder trio may need to wait for another game.
Xehanort

Kingdom Hearts 4 has a lot of loose threads to pull on, like Skuld’s whereabouts, the Nameless Star’s body, what’s in the Black Box, and so on, but this is also not a series that’s afraid of drawing on its old ideas. As Strelitzia shows, characters once thought dead or part of seemingly resolved storylines can return in Kingdom Hearts 4, including Xehanort himself. Thanks to some Tetsuya Nomura artwork, a young iteration of Xehanort has been theorized to be returning on Sora’s side, and it’s hard to deny Kingdom Hearts’ first main villain a chance to stick around until the series’ real finale.
Luxord

Quadratum, and the Lost Master Arc itself, have already begun building a stable of related characters that should appear in Kingdom Hearts 4. The Master of Masters, Luxu, and the Foretellers should be stepping in as the new antagonist faction, while KH3: ReMind’s Yozora should be around to serve as a parallel protagonist to Sora. However, Luxord’s Somebody is also implied to be a Quadratum inhabitant in ReMind, and a suspicious amount of attention was also drawn to Luxord across KH3 and its DLC. Even among other Organization XIII members observed to have Keyblade wielder heritage, Luxord has the best shot at beating the odds and slipping into Kingdom Hearts 4.