Here, is the point in the story where the games began their tail of adventure and wonderers strain between those things that reflected darkness and bloom with light in the worlds; but this in fact is the second part of the story.
The years that fell away from the memory of the Key blade War, a new kind of darkness had grown; a new threat, but still by the same dark puppetries that trifled over Terra, Aqua and Ventus. Even those who had no part in it the first time around, now share amongst the discovering of a hearts driven power when taken apart.
Instead of inverse; heartless and nobodys take to the stage of threating the safety of the Seven Princesses of heart; as their untainted hearts hold the key to succeed where those had failed.
As darkness had fallen over the worlds,pulling them out of sight from the sky and eventually reaching the Destiny islands. The home of Riku, Sora and Kairi;(After she moved from the Radiant Garden) also home to other Fantasy characters, ofmuch younger versions of themselves.
As a storm had taken the island one night, Sora finds that both Riku and Kairi had gone to save the raft that they had made together. But as Sora quickly finds Riku, choosing to step into the darkness that consumed his home, Sora is presented with a Key blade to defend himself.
Not understanding what was happening, after Riku had suddenly disappeared; Sora searched the island for Kairi. But all he finds is what seems to be a memory of her. Not realizing that it is her heart taking refuge in his own heart. Just like Ventus.
Soon enough the island is lost, but Sora is sent to Traverse town instead of becoming with the darkness.
Later on and even more so in the game ‘Drop Dream Distance’, the purpose of Traverse Town finally becomes clear. As it is a refuge for those who have become lost, but avoided being trapped in the spaces between worlds and lost in the realm of darkness.
This is where Sora learns of the heartless and what it means to have the key blade, while meeting new and unique people; including having his first in counter with his long life friends, Donald and Goofy. Sora chooses to go with Goofy and Donald to others world in hope that maybe along the way, he would find both Riku and Kairi.
When Sora dose find Riku, quickly Riku finds himself feeling left out of the pitcher. Confronted by Sora’s ‘new’ friends and the possibility that Sora had changed and forgotten about him and Kairi.
Riku takes off on his own to save her, while becoming unaware of the influence that the darkness was having on him. As the control over Riku grow ever so strongly within each step that he took away from Sora.
Once both Riku and Sora met up again, Sora realized the horrible act that Riku planned to do; by stealing Pinocchio’s heart and giving it to Kairi. But Riku doesn’t succeed thanks to Sora, so he waits for Sora on the Jolly Roger with Kairi’s body.
Easily enough Sora finds the Jolly Roger and is faced with Riku’s new dark powers. Defeated and throne to the brig of the ship, Sora meets Peter Pan and Tink a bell; which helped Sora and his friends escape. Riku aborts the ship and transport Kairi to Hallow Bastion; where the six other Princesses lay in sleep.
Here a challenge between Riku and Sora unravels over the key blade; essentially Riku dose take the Key Blade since it is by right his. But Sora regains it back with the will and strength of his heart, pure light over the darkness.
Out of fear, Riku is encountered by a figure, which is an older Ansem who opens Riku’s heart and consumes it, controlling it.
This dose quickly become confusing as what you know of Ansem, is that he is Ansem the wise, as you leant to be a scientist. But if you recall, he had taken the new Xehatnort under his wing. At this point, Ansem the wise is no more; his identity taken by Xehanort. He quickly becomes a character called Dez.
Now the new Ansem is of a heartless and a nobody of apprentice Xehanort. How? Bear with me.
A heartless is the person themselves that has lost there heart and a Nobody is a creature that forms once a heartless is created.
Once apprentice Xehatnort create an evil like personality and started experimenting on the darkness with in hearts, he too gave in completely to the darkness. Creating his own Heartless and Nobody, but he was still able to keep them both in human form. The other way a Nobody can suddenly be reborn into a human form, is if their heartless was returned to their human form.
So there is no apprentice Ansem, there is Heartless Ansem and Nobody Xemnas. The one that confronted Riku was an older version of Ansem, (since having the power to travel into the past) he was trying to change events to prevent his defeat later on in the games. Essentially he places the present Ansem, into Riku.
Once Ansem has Riku, Riku no longer has any control of his actions; he is now Ansem, the seeker of darkness.
Once Sora realizes this, he tries to fight Ansem to release Riku from him and to get to Kairi. But all he does is wounded him and he runs off. Right now Sora can’t help Riku so he tries Kairi. Ansem himself told Sora that Kairi’s heart was inside him and that the key whole cannot be unlocked as long as he had it. Neither would she ever wake from her sleep.
So with using Ansem’s Key Blade Sora unlocks his own heart and returns Kairi’s heart, this also allows the other six Princesses to wake from their slumber. But what Sora didn’t count was that once he unlocked his heart, he would turn into a heartless.
Kairi, who is now awake, swears that she would find a way to save him. But suddenly Ansem appears again, wanting to take Kairi and unlock the door; however what little strength Riku has left, is lit by the sight of Kairi.His able to keep him from her andseparate himself from Ansem.
Kairi, Donald and Goofy run from the castle as it starts to become over run by endless heartless; but just before their free Kairi notice that a single Heartless was following them and completely harmless. It’s Sora.
When surrounded, Kairi defense Sora but fails, instead without realizing Kairi uses her power of light and recreates Sora. Returning him to Human form and there the key blade protects them both.
(Don’t forget what I just said before about Heartless and Nobodys.)
Once Sora had got Kairi to Traverse Town and under the protection of Leon, he went out to take on Ansem and after an endless struggle of fighting with him; outside the door of the Kingdom Hearts, Ansem was suddenly struck by the inner light from the door as he opened it. A light that Sora engages,destroyingAnsem.
Only problem now, was that the door was open and the trio couldn’t close it. Suddenly, both Riku and King Mickey appear on the other side of the door, helping them to close it. But Sora doesn't want to leave Riku, however Mickey in shores Sora that he will get them both out of the darkness.
Once the door was closed and that Ansem was gone the worlds that fall away into the darkness started to slowly rebuild and return back to there place in the sky.
In the distance Sora can see Kairi on the beach of their home. He goes to her, but he can’t go with her. He tells her that he would return to her, with Riku and she believes he will.
What happens from this point on, the fates of other hearts start to intertwine; all because of Sora and Kairi.
As it has been said; The closer you get to the light, the greater your shadow will be.