Kingdom Hearts is one of the ongoing Square Enix franchises that predates the Square and Enix merger as development started under Square Soft, which means we've had enough time to absolutely forget the storyline. We've had two main games, five spin-off games that function as prequel, sequel, and in-between stories. And now, over 10 years after the release of Kingdom Hearts II, we're finally getting the third game in the main franchise.
Which begs the question: What even is Kingdom Hearts about?
The short answer is that the game is a story about the ongoing struggle between the forces of light and dark spread across a variety of Disney properties with cameos by various Final Fantasy heroes and villains. The story's main villain, Xehanort, is attempting to recreate an old war that split all of the worlds apart, because he's super evil like that.
The long answer is incredibly complicated. Not even the Wikipedia summary happens to make a lot of sense. So, we're going to do our absolute best to provide the KH plotline for you, in chronological order.
Of course, you can always wait until launch day and sit through the plot summary cutscenes, but why waste time watching that when you first get your hands on the game? Also, as someone with access to an early copy of the game – the recap cutscenes in Kingdom Hearts III are pretty darn useless at figuring out anything more in-depth than "something something darkness, something something keyblades."
The first game in the series tells the story of a boy named Sora who grew up on a world called the Destiny Islands, with his best friends Kairi and Riku. However, Kairi is not native to the Destiny Islands, she'd washed up there as a child, which leads the three kids to theorize that there are other worlds out there. They plan to make a raft to sail off to the other worlds and get off their tiny island. The night before they're supposed to leave, Riku opens a spooky door in a cave on the island, which unleashes a hoard of heartless onto the islands. Sora, sensing something was up, arrives just a bit too late and finds Riku just as he's swallowed by a tide of shadows and disappears. Sora finds himself a mystical weapon called the Keyblade and battles with the heartless before the Destiny Islands are destroyed and he ends up in a different world. Sora finds new friends in Donald and Goofy, who are looking for their missing King (Mickey Mouse), who told them to find the master of the Keyblade. Sora, Donald, and Goofy make friends with Final Fantasy VII's Aerith and Yuffie as well as Final Fantasy VIII's Squall (who insists on going by Leon, because Squall was too edgy, we guess?). From there, the three go on to face various Disney villains on worlds modeled after classic movies like The Little Mermaid, Aladdin, Alice in Wonderland, and even The Nightmare Before Christmas.
On each world, Sora is tasked with taking down the world boss and then "locking" the heart of the world with his Keyblade. During his journey, Sora is reunited with both Riku and Kairi, though Riku has aligned himself with the forces of darkness in order to save Kairi, who has gone into a catatonic state without her heart. Riku is working with Maleficent to gather the Princesses of Heart in order to further Maleficent's goal of total world domination. After Riku unleashes the "unlocked" version of Maleficent, which is her dragon form, Sora confronts his best friend only to find out two things: Riku has been possessed by someone who calls himself "Ansem, the Keeper of Darkness" and Kairi has hidden her heart in Sora. Because hearts are metaphysical things like souls and you can just transfer yours to another person. Unlocking Kairi's heart from within Sora turns the hero into a heartless for a bit, before he's back to his old self (this minor detail is weirldy important for future games, keep in mind). From there, Sora returns to the desiccated remains of the Destiny Islands to confront Ansem, and eventually makes his way to a massive white doorway that separates the world as everyone knows it from the realm known as Kingdom Hearts. The Door to Darkness was opened by Maleficent and Ansem, and Sora's ultimate task in the game is to close it. Sora closes the door with the help of King Mickey and a no-longer-possessed Riku.
Kingdom Hearts: Chain of Memories
This is where Chain of Memories kicks in, because Mickey and Riku were on the wrong side of the Door to Darkness, and Sora wants to get all his friends back. Sora, Donald, and Goofy go searching for their missing King and best friend/ rival in a place called Castle Oblivion. When they enter the castle, they forget all their abilities for a very convenient new-game nerf. While they travel through the castle, they lose more memories, but also pick up new memories as well. Sora faces off against a series of people in hoods who call themselves "The Organization" and test Sora based on his memories of past battles. As Sora loses his memories, he starts to remember a girl named Namine. He then fights a replica of Riku (though both Sora and Riku Replica think the replica is the real Riku). Organization member and double-agent Axel, meanwhile, releases Namine and she tells Sora that she was the one manipulating his memories because the Lord of Castle Oblivion, Marluxia, lured Sora to the castle as a way to overthrow the rest of the Organization. After Sora defeats Marluxia, Namine puts Sora, Goofy, and Donald into pods so they can recover their lost memories. However, they will lose their new memories to compensate. Sora believes he will remember Namine regardless, because his memories of her will be stored in his heart, because EVERYTHING IS ABOUT HEARTS YOU GUYS.
While all this was happening, King Mickey and Riku ended up in the Castle themselves for the events of Reverse/Rebirth. Riku was dropped in the basement to learn how to combat his inner darkness while fighting off members of Organization XIII like Vexen, Lexaeus, and Zexion . However, Riku was having some trouble throwing off the whole body-possession thing, and ended up battling a ton of the Organization himself. Once Sora is safe in his pod, Riku is saved from being nearly killed by overexposure to the Light by Namine, disguised as Kairi. Riku and the King come across a creepy man in a frankly ridiculous mask called DiZ, who tells them to seek out Namine. Namine tells Riku that Ansem keeps trying to possess him because Ansem is stored in his heart, so Riku decides the best option is to go smack Ansem in the face with his weird wing keyblade. After trying to literally beat the darkness out of himself, Riku and King Mickey decide to leave Castle Oblivion and go on a journey so Riku can learn to be a red mage.
Kingdom Hearts II
Kingdom Hearts II takes place a year later, as Sora, Donald, and Goofy had been chilling in suspended animation to recover their lost memories. Because Sora became a heartless for a brief bit during the end of Kingdom Hearts, he has a "Nobody." Which is the husk of a body remaining after the person's heart has become consumed by darkness and made into a heartless. However, because Sora unlocked Kairi's heart as well as his own, he also created another Nobody, this one for Kairi. Roxas was Sora's Nobody, while Namine was Kairi's. In an attempt to merge Roxas with Sora, DiZ dropped Roxas in a virtual simulation of Twilight Town. Prior to this, Roxas was hanging out with The Organization (also known as Organization XIII), and befriended Axel. Axel and other Nobodies infiltrated the virtual Twilight Town to try and save his buddy, however, Roxas pushes back the Nobodies and finishes merging with Sora.
From there, Sora, Donald, and Goofy awaken in Twilight Town and meet up with King Mickey and the sorcerer from Fantasia, Yen Sid. The trio are then sent on another journey across various Disney worlds to find Riku and uncover Organization XIII's plans. Maleficent is resurrected as well, because you can't keep a good dragon witch down. At a later point in their journey, Mickey reveals to Sora and Pals that the man they knew as Ansem is in fact an imposter named Xehanort, and his Nobody Xemnas is the leader of Organization XIII. The Organization wanted to use the power of Kingdom Hearts to regain their lost hearts. Axel sacrifices himself to give Sora, Donald, and Goofy a way into the headquarters of the Organization. In The World That Never Was, Sora finds Kairi and Riku (Riku now looking like Xehanort's Heartless, because the poor boy couldn't even get possessed by actual Xehanort) while Mickey meets with DiZ, who was actually the real-deal Ansem. Ansem, who was Xehanort's mentor, uses a device that dissipates some of Kingdom Hearts' power but a system overload self-destructs the device and it engulfs both Ansem and returns Riku to his original form. Sora and company then lay a beat down on Xemnas, who uses the remains of Kingdom Hearts' power to make multiple versions of himself. Once Sora and Riku destroy Xemnas, they're dropped back on the Destiny Islands with Kairi. A post-credits scene showed the three reading a letter from King Mickey.
Kingdom Hearts Coded
Kingdom Hearts Coded (remastered as Kingdom Hearts Re:coded) is a puzzle-based handheld spinoff, that takes place right after Kingdom Hearts II. The story is pretty simple: Jiminy Cricket was going through his journals about Sora's battles with Organization XIII and found two messages he doesn't remember writing. The first message implies that Sora, Donald, and Goofy must return to the worlds of past games to save them again. King Mickey digitizes the journals and then Sora, Goofy, Donald, and Mickey all go into the data world. While the majority of Coded's plot is mostly time-killing fluff about programming bugs, it does have a couple surprises that lead to future games. At the end of the debug sessions, the data world version of Namine reveals that she was the one to add the two messages to Jiminy Cricket's journals, and the bugs were an accident. Her second message implies that Sora needs to find and save herself, Roxas, Axel, Xion, Terra, Aqua, and Ventus. The message Mickey sends to Sora at the end of Kingdom Hearts II is Namine's note about who he needs to save.
In a post-credit sequence exclusive to Re:coded, Mickey and Yen Sid discuss where Terra, Aqua, and Ventus could be. This takes us to Birth by Sleep. Yen Sid also mentions that with the destruction of both Xehanort's Heartless and Xemnas, Master Xehanort will likely return. In a secret ending exclusive to the Kingdom Hearts HD 2.5 ReMIX cinematic version, Braig (the person who became Organization XIII member Xigbar) is restored to human form along with several other Organization XIII members, and the group talks with a younger, time-travelling version of Xehanort about the location of his older self. Braig asks Young Xehanort who to bring along with him, and this leads us to Dream Drop Distance, eventually.
Kingdom Hearts 358/2 Days
Kingdom Hearts 358/2 Days is the fifth game in the series, but the story occurs during the end of Kingdom Hearts and runs parallel to Chain of Memories. The game focuses on Roxas's life with Organization XIII and his relationship with fellow Organization members Axel and Xion. Xemnas found Roxas in Twilight Town and recruited him to Organization XIII, though Roxas lacks the memories of his original self unlike other Nobodies. Roxas is sent on missions to other worlds, either alone or with another Organization member, to destroy vast quantities of Heartless and release their stolen hearts with his Keyblade. This adds more hearts to Kingdom Hearts, so Xemnas can use them in his ultimate plan to get the Nobodies their bodies back. Roxas quickly becomes friends with Axel, who functions as his mentor in the Organization, but after Axel and several other Organization members are assigned to Castle Oblivion, Roxas partners up with the group's newest member, Xion. Xion becomes friends with Roxas and Axel, and the three spend way too much time sitting on clock towers and eating sea-salt ice cream.
After failing to kill Riku in the basement of Castle Oblivion (a fight we don't see in Chain of Memories), Xion falls into a coma. Xion begins to question her own existence after having visions of Sora when she wakes from her coma. She discovers that she is an artifical replica created by Xemnas as a way to control Roxas and prevent Sora from waking, because her purpose is to absorb Roxas and become a perfect copy of Sora. She decides to escape the Organization when she begins siphoning Roxas' strength, and while Axel allows her to escape, it costs him Roxas' trust. After learning about Xion's true identity from Xemnas, Roxas leaves the organization and confronts Xion. After Roxas defeats her, Xion merges with Sora, which causes all knowledge of her existence to vanish.
Roxas goes to the World That Never Was to stop Xemnas according to Xion's last wish, but encounters Riku. Riku attempts to capture Roxas in order to bring him to DiZ and complete Sora's memory restoration. Roxas kicks Riku's butt until Riku uses the power of darkness in his own heart, which makes him look like Xehanort's Heartless. Once captured, Roxas is dropped into a virtual simulation of Twilight Town without his memories of the Organization so that he can merge with Sora.
Kingdom Hearts Birth By Sleep
If all that wasn't weird enough, we're now entering the prequel stage of Kingdom Hearts lore, with Birth by Sleep. The game tells the story of a familiar-looking trio of friends who are all keyblade wielders: Aqua, Venuts, and Terra. The game begins with Master Xehanort bringing a comatose Ventus to the Destiny Islands after his heart is damaged. A newborn heart connects with Ventus's heart and heals him. Three guesses who that was (and the first two don't count). Years later, Terra and Aqua are taking an exam to achieve the Mark of Mastery, though Xehanort manipulates the exam so Terra fails and Aqua passes, all because he wants to lessen Terra's control on the darkness in his heart (sound familiar?). After the exam, Xehanort disappears and a hord of Unversed appear through the world, so Master Eraqus sends Terra and Aqua to destroy the Unversed and find Xehanort across multiple worlds. Meanwhile, Ventus follows Terra against Master Eraqus's wishes. Aqua is tasked with monitoring Terra's darkness and bringing Ventus back to the Land of Departure.
As the three travel throughout the worlds, Terra attracts the attention of several villains who attempt to sway him to their side with knowledge about Xehanort. Terra finds Xehanort, who offers to take Terra as an apprentice and teach him to use his inner darkness to gain power. Xehanort also instructs Terra to destroy Vanitas as the source of the Unversed. While the trio of friends meet up again, they've got some serious problems. Ventus confronts Xehanort and learns that his plan is to recombine Ventus and Vanitas's hearts in order to create an all-powerful keyblade called the χ-blade. Eraqus attempts to kill Ventus to foil Xehanort's plot, but is stopped when Terra interrupts the fight to save Ventus. After Eraqus is klled by Xehanort, Terra, Ventus, and Aqua are all to the Keyblade Graveyard. At the Graveyard, both Xehanort and Vanitas reveal their plan to use the χ-blade to unlock Kingdom Hearts and start a new Keyblade War. Terra's heart is swallowed by the darkness, and Xehanort takes over his body to replace his aging one. The possession is entirely complete, but Terra's mind remains within his discarded suit of armor which comes to life and defeats Xehanort. Meanwhile, Ventus is forced to merge with Vanitas and create the χ-blade, and both Aqua and Mickey fight with the possessed Vantus and destroy the keyblade, while Ventus and Vanitas have a battle within Ventus's own mind. However, because of the mental duel, Ventus loses his heart and falls into a catatonic state.
Aqua brings Ventus's body to the Land of Departure, which she transforms into Castle Oblivion to ensure Ventus will not be disturbed. When Aqua fights the possessed Terra, Xehanort impales himself on his own keyblade which drops Terra into the realm of darkness. While Aqua rescues Terra, she is trapped in the darkness in the process. Ansem (the real Ansem, aka DiZ) finds an amnesiac version of Xehanort still possessing Terra's body, while Ventus's heart reconnects with Sora's and sticks it out inside of Sora. Aqua meets Ansem in the realm of darkness, and learns about Sora's abilities to save those connected to himself.
Kingdom Hearts 3D: Dream Drop Distance
Dream Drop Distance is both a prequel involving time-travel, and a midway point between Kingdom Hearts II and Kingdom Hearts III. Sora and Riku are put through a Mark of Mastery exam to give them the power to rescue their missing allies and counter Master Xehanort. The boys needed to head to seven worlds and unlock their keyholes in order to fully restore them to the realm of light. There's also some fun gameplay involving benevolent "Spirit" Dream Eaters and "Nightmare" Dream Eaters that infest the sleeping worlds. In order to enter the sleeping worlds, Sora and Riku are sent back in time to their homeworld's destruction. The two are separated at the start of the test, and repeatedly encounter a kid accompanied by either Xemnas (for Sora) or Ansem (for Riku).
Once the exam is completed, Sora and Riku arrive in the World that Never Was instead of the realm of light, because the mystery boy lured Sora into a trap. Sora is dropped into a deep sleep where he defeats Xemnas within his own dreams, but his heart is swallowed by darkness, encased in Ventus's armor for protection. Meanwhile, Ansem reveals that Riku has spent the exam travelling through Sora's dreams as a Dream Eater. After defeating Ansem, Riku learns that the mystery kid is actually Young Xehanort. Young Xehanort is planning to create a new Organization XIII, comprised of thirteen different incarnations of Xehanort from across time, including the hosts of his fragmented heart. A revived Master Xehanort appears and attempts to turn Sora into his final host, so he can pit his thirteen "seekers of darkness" against the seven "guardians of light" in order to create the χ-blade. Again. Xehanort is foiled when Lea (the full person version of Axel), rescues Sora. Xehanort and his various incarnations fade back into their original time-periods.
Riku returns to Yen Sid's tower and decides to enter the world of dreams again to releases Sora's heart from Ventus's armor. Riku then arrives in a simulation of the Destiny Islands and meets a virtual copy of Ansem the Wise (the real Ansem), who gives him data he left in Sora's heart. When Riku returns to the realm of light, Yen Sid commends Riku and declares him a Keyblade Master. Lea is also revealed to be a Keyblade wielder, who intends to become a Master as well. Sora returns to the sleeping worlds to try and gain his Mark of Mastery again. In the secret ending, Yen Sid reveals his plan to gather seven Keyblad wielders to prevent Xehanort from using the Princesses of Heart to forge the χ-blade. So Riku recruits Kairi to be trained as a Keyblade wielder as well.
After Dream Drop Distance, there's Kingdom Hearts χ, which was released outside of Japan as Kingdom Hearts: Unchained χ, and later rebranded as Kingdom Hearts: Union χ [Cross]. The mobile game tells the story of the first Keyblade War, which is what Xehanort hopes to reignite by creating the χ-blade.
However, all you really need to know about that for Kingdom Hearts III is that it was an apocalyptic war.