Two recurring themes populate the Kingdom Hearts series: 1. True power comes from friendship and connections with others 2. Women are useless

The protagonist of the game is Sora, but first, background: Kingdom Hearts is the heart of all worlds and a source of immense power. It is controlled by a weapon called the x-blade (not to be confused with keyblade), which acts as its key. Long ago thousands of people used keyblades (not to be confused with the x-blade), magical weapons that can lock and unlock stuff and also have lots of other powers, to fight for control of the x-blade (not to be confused with the keyblades, which they already had). In the process the world was split into lots of different pieces which were then walled off from each other with a substance called gummi.

In the less-distant past, Xehanort, a boy from Destiny Islands, escapes his tiny world and becomes a keyblade master in his own right. He learned that there are many worlds (which is supposed to be a secret) because Xehanort-from-the-present sends a version of himself back in time to tell him about it and then tells him to travel to a bunch of different places because time travel requires that a version of one’s self must be present at the time and place. More on that later.

He’s friends with Eraqus and Yen Sid who are also keyblade masters, but then they aren’t friends anymore because Xehanort is evil (but later he pretends to be good). Xehanort wants to obtain the x-blade (not keyblade) so he can use Kingdom Hearts to get lots of power. Yen Sid trains Mickey to be a keyblade master, Eraqus trains Terra and Aqua, and Xehanort trains Ventus, but then he takes all the darkness out of Ventus’s heart and turns it into Vanitas and dumps Ventus with Eraqus in the Land of Departure, which exists on the border between the Realm of Light (where pretty much the entire series happens) and the Realm of Darkness, which is made of darkness.

Xehanort has a two-part plan with Eraqus’s pupils. 1. Get Terra the gullible dupe to succumb to the darkness in his heart so that Xehanort can take over his body, and 2. Get Ventus to become stronger so that he and Vanitas can fight; he believes the clash of pure light and pure darkness will re-create the x-blade. He also kills Eraqus in the process. Aqua, being a useless woman, tries and fails to get Ventus to return home and to prevent Terra from falling to the darkness. When she tries to free Terra’s body from Xehanort’s control, she fails so hard she gets trapped in the Realm of Darkness. Before that, however, in an act of non-useless womanness unparallelled in the series, she and Mickey manage to break the imperfect x-blade with her keyblade. This really messes up Ven (since it was made from his heart), so she transforms the Land of Departure into Castle Oblivion so that no one can use it to upset the balance of the Realms and so that Ven’s body has a place to recover. In the meantime, Ven unconsciously shoves his heart into Sora, and Xehanort is taken in as the apprentice of Ansem the Wise, the ruler of Radiant Garden.

This all happens ten years before the start of the series proper. A year later, Xehanort learns about the Heartless, creatures of pure darkness born when someone’s heart is stolen from his or her body. (If the person has a strong will, this also creates a Nobody left over from their lifeless body and they retain their sentience as a Heartless if they become one voluntarily). Xehanort gets Xehanort’s other apprentices and some castle guards to overthrow Ansem and trap him in the Realm of Darkness, and then Xehanort takes Ansem’s name. The exact reason for this isn’t given, but if my name was Xehanort, I’d want to change it too. Then he split himself into a Heartless and a Nobody (in the process, doing the same to those other apprentices) for another two-point plan.

1. Time travel is hard but it’s easier when you don’t have a body, so Heartless-Xehanort (aka Ansem, Seeker of Darkness) travels back in time to tell young Xehanort that stuff I mentioned before, then returns to the present to look for Kingdom Hearts and corrupt the hearts of various world to plunge them into darkness. 2. As part of his new plan to create the x-blade, he wants seven hearts of light and thirteen hearts of darkness. Nobody-Xehanort (aka Xemnas) creates an organization to gather thirteen powerful Nobodies to create those hearts of Darkness. Xemnas, Xemnas’s lackey Braig, and those other apprentices become the first members of Organization XIII. The outpouring of Heartless turns Radiant Garden into Hollow Bastion, and then Maleficent moves in like a hermit crab and basically takes credit for Xehanort’s evil. The citizens of Radiant Garden are either turned into Heartless or wind up in a place called Traverse Town that seems to exist just for this.

FINALLY, we get to the beginning of Kingdom Hearts. The series follows protagonist Sora, his best friend Riku (whom Terra had chosen as his keyblade successor), and his aggressively useless love interest Kairi. Literally all Kairi has to do to fulfill her role in the preservation of the world is stay alive, and she doesn’t even do that right. They all live on Destiny Islands together until Ansem comes and fucks shit up. In the process Kairi’s heart is removed and then shoved into Sora. This creates the Nobody Namine, who becomes important later. Riku starts giving in to the darkness so Terra’s keyblade chooses to stick with Sora instead. Meanwhile, Mickey goes to the Realm of Darkness without warning and tells his subjects Donald and Goofy to go find the keyblade wielder; Pluto tags along. Minnie and Daisy stay behind because they are more useless than Pluto.

Sora winds up in Traverse Town and joins up with Donald and Goofy (who are able to travel between worlds because they have a ship made from gummi), while Riku winds up in Hollow Bastion and Maleficent turns him into her new apprentice and manipulates him towards evil. Sora travels to a bunch of different Disney worlds and beating up baddies and locking the worlds’ hearts so that darkness can’t destroy them like it did to Destiny Island and others. At the same time, Maleficent is gathering the Seven Princesses of Hearts, who have hearts free from darkness, and Riku finds Kairi’s body. Eventually Sora winds up in Hollow Bastion where Riku tells him the Keyblade was meant for him and so he takes it and blah blah blah it turns out the real power was friendship and Sora gets the Keyblade back, like, an hour later.

After this, Riku is so embarrassed that he lets Heartless-Xehanort take over his body. He forms a special fake keyblade from the six princess hearts Maleficent gathered that can unlock people’s hearts. Heartless-Xehanort-Ansem-Riku tells Sora that Kairi is the seventh princess (from Radiant Garden, originally; Aqua cast a spell to keep Kairi safe by sending her to Destiny Islands, and then it stopped working in time for Destiny Islands to be destroyed too since Aqua is a woman) and that her heart is shoved inside Sora’s body. Then Sora beats Riku like a red-headed step-child and uses the fake keyblade to release his heart; this creates a conscious Heartless and also a Nobody called Roxas, who again will become important later. Sora’s Heartless finds Kairi and turns back into a person.

There are multiple types of Kingdom Hearts, and Heartless-Xehanort has been plunging worlds into darkness to create a Kingdom Hearts made from the hearts of worlds (which is yellow). Nobody-Xehanort, meanwhile, is trying to create a Kingdom Hearts made from the hearts of people (which is blue), since when a heartless is destroyed by a keyblade, it gets added to that Kingdom Hearts. More on that later. Sora follows Heartless-Xehanort to the Kingdom Hearts of worlds and beats him up; Riku and Mickey are on the Realm of Darkness side, and Sora, Riku, and Mickey seal yellow Kingdom Hearts (which is a moon shaped like a heart but it’s also a door at the same time), which returns the worlds Heartless-Xehanort destroyed to the Realm of Light, except for a few, which are kinda stuck in between as “sleeping worlds”.

Organization XIII, by the way, now includes Roxas, and they’re using him to keep capturing hearts for their Kingdom Hearts; Roxas can wield Ven’s keyblade, so Xemnas uses him to help make blue Kingdom Hearts. Also, remember Namine, from earlier? Well, she’s also a Nobody, but she’s not a member of Organization XIII, but she does have the power to manipulate Sora’s memories for some reason. They also make an artificial replica of Sora called Xion who can also wield the keyblade for reasons that make less sense.

Sora, Riku, and MIckey all wind up in Castle Oblivion--Riku and Mickey in the basement, Sora, Donald, and Goofy on the ground floor. Xemnas has sent several members of Organization XIII to Castle Oblivion, where he intends to use Axel, Sora, and RIku to kill off the members he thinks are too weak or too strongheaded to become his vessels. This obviously includes the Organization’s only female member, because she is a woman, and therefore useless. Meanwhile, one of those Organization members is using Namine to manipulate Sora by implanting false memories so that Marluxia can use Sora to seize control of Organization XIII. It doesn’t work and Marluxia dies. Riku, meanwhile, spends this time fighting the darkness in his heart but later learns to control it instead. He also finds Ansem the Wise, who’s going through a bit of a goth phase and so he wears a mask made of a belt and insists people call him DiZ. Riku, MIckey, and DiZ made their way back from the Realm of Darkness while Aqua did not because they are men, and therefore not useless.

At the end, Namine decides to help Sora, but at this point his memories are so scrambled that she has to put him to sleep for almost a full year and put the pieces back together. Organization XIII uses Roxas and Xion as vessels to contain Sora’s memories, ensuring he can’t wake back up until they rejoin him. While this is going on, Roxas, Xion, and Axel are all becoming best buds (with lots of homoerotic overtones, even measured against the pretty homoerotic background radiation of the series), but when Xion dies so she can shove her heart into Sora’s body, the nature of her existence means everyone eventually forgets she ever existed, which is convenient. Roxas is POed by all this business and goes to give Xemnas a piece of his mind, but he’s intercepted by Riku, who knocks him out and drags him back to DiZ so his heart can be shoved in Sora’s body, too. However, Riku has to give into the darkness completely and so he looks like Heartless-Xehanort for a while.

Oh, also during this time, DiZ is shoving data into Sora’s heart, and that makes Data-Sora, who manages to gain his own consciousness, which eventually tips DiZ off that Nobodies can create their own hearts, but otherwise doesn’t amount to much. He stores Roxas in a data replica of a place called Twilight Town for the last week while they finalize waking up Sora.

So then Sora, Donald, and Goofy wake up (for some reason they didn’t wake up Donald and Goofy even though they weren’t split into multiple pieces that had to be reunited; I guess they just kinda forgot about them), and they party through a bunch of Disney worlds again once Yen Sid gives them back a new gummi ship. Hollow Bastion is being turned back into Radiant Garden, Sora travels back in time at Disney Castle despite there not being a version of himself at the destination which is supposed to be impossible but they kinda forget about that, and then they find out the Organization’s plan. But they figure they can’t stop killing Heartless, so they just keep doing that. The Organization kidnaps Kairi for no real reason, Maleficent is brought back to life but doesn’t really do much, and eventually they make their way to the Organization’s world. Axel sacrifices himself to save Sora from a bunch of easily-slain monsters because Sora contains his “best friend” Roxas.

Sora meets up with Heartless-Xehanort-Riku, they kill the rest of the members of the Organization, Kairi is also there, and then DiZ uses a machine he built to try to drain the harts from blue Kingdom Hearts. The device explodes, and as a result: Heartless-Xehanort-Riku is turned back into Riku-Riku, his evil sword is turned into a keyblade of his very own, and DiZ is sent into the Realm of Darkness again, where he eventually bumps into Aqua. Xemnas tries to use the now-incomplete blue Kingdom Hearts to turn himself into a god, but Sora and Riku follow him and kill him.

Later, Yen Sid tests Sora and Riku to become proper Keyblade Masters, given the task of diving into the world of dreams and reviving those worlds I mentioned that weren’t quiiiiiite brought back when yellow Kingdom Hearts was sealed, since they’re infested with monsters called Dream Eaters. But young Xehanort, traveling in time, shoves Riku into Sora’s dream world. We find out that the TRUE and HONEST Organization XIII is composed mostly of copies of Xehanort from different periods in time, though this does include a couple members of the FAKE Organization XIII. By the way, since both the Heartless and Nobodies of the other Organization members were destroyed, they got revived, which also happened to Xehanort, apparently. Now, Xehanort traps Sora in a dream world so that he can turn Sora into his thirteenth vessel, instead of Riku, the guy who’s already accepted Xehanort into his heart once, has way more darkness in his heart, and is arguably stronger. Riku has gotten out of Sora’s dream-of-a-dream back into the real world and stops this from happening along with Mickey, Donald, and Goofy. Then he shoves himself into Sora’s heart one more time and wakes him up, so Yen Sid says Riku is a keyblade master but Sora isn’t even though they both fulfilled the outlined criteria of the test.

The end, until the next game comes out.