Kingdom Hearts Explained

Heres another random sort of explaination

The three main games in the Kingdom Hearts series focus on the adventures of Sora and his friends, Kairi and Riku. Appearing as the series prequel, Kingdom Hearts: Birth by Sleep, Kairi, Riku and Sora respectively encounter three figures named Aqua, Terra, and Ventus. As the three children go on their lives, eventually meeting each other, Terra, Aqua and Ventus suffer horrific, punishing fates that indirectly influence the three children.
The first game, picking up ten years later, shows how Sora is separated from his friends when their world, Destiny Islands, is invaded by creatures known as the Heartless. During the invasion, Sora obtains a weapon to be able to fight off the Heartless, known as the Keyblade. Soon after finding himself in Traverse Town, Sora meets Donald Duck and Goofy, two emissaries from Disney Castle sent by King Mickey to find the wielder of the mysterious weapon, the Keyblade.[54][55] The three band together and travel to different Disney-themed worlds, sealing the hearts of the worlds to prevent more Heartless invasions. Along the way, they encounter a group of Disney villains, led by Maleficent, who is controlling the Heartless.[56][57] Though they eventually defeat Maleficent, the three discover that a man named Ansem is the true antagonist. Ansem's plan is to open the door to "Kingdom Hearts" in the hopes of attaining eternal darkness. Sora, Donald, and Goofy defeat Ansem, and seal the door with the help of Riku and King Mickey on the other side of the door
After sealing the door to Kingdom Hearts, the three begin searching for Riku and King Mickey, finding themselves heading towards a mysterious fortress called Castle Oblivion.[58][59] Upon entering the fortress, they begin to lose their memories.[60] The three encounter a group of dark hooded villains, part of a mysterious Organization. In the castle, Sora learns his memories have been manipulated by a girl named Naminé who was being held captive by the Organization. To allow them to regain their memories, Naminé puts Sora, Donald, and Goofy to sleep for a year; in the process, they must lose the memories of their experience in Castle Oblivion.[61] At the same time, Riku finds himself in the basement of the castle and begins traveling to the first floor with the aid of King Mickey. Riku fights both the Organization's members and the darkness in his heart, learning to accept his dual nature between light and dark.[62] Allying himself with the mysterious DiZ, Riku aids him in keeping Sora and Naminé until the former is awoken. However a snag in the plan over the year forces Riku to go after a young man named Roxas, the thirteenth member of the Organization, to enable Sora's reawakening.
Seven days after Riku's success, Sora, Donald, and Goofy awaken in Twilight Town, with no memory of their time at Castle Oblivion, and resume their search for Riku and King Mickey. They learn of the Nobodies and are re-familiarized with their leaders, Organization XIII. Afterwards, Maleficent is resurrected and joins with Pete, another Disney villain, to find a new base of operations before resuming her quest for power and revenge on Sora. Sora once again travels to many Disney-themed worlds and resolves the troubles caused by not just Maleficent and Pete, but also Organization XIII whose members refer to him as Roxas. Meanwhile, Kairi is kidnapped by the Organization. They meet King Mickey, who reveals that the "Ansem" Sora defeated was actually the Heartless of Xehanort, a student of the real Ansem the Wise. Xemnas, the leader of Organization XIII, reveals himself to be the Nobody of Xehanort.[63][64] The three arrive at the headquarters of Organization XIII, with Kingdom Hearts looming overhead, with Sora defeating all the Organization members as he is finally reunited with Kairi and Riku, who reveals Roxas as Sora's Nobody whom he captured by willingly assuming Ansem's form(Xehanort's heartless) so Roxas would be integrated back into Sora. While this occurred, Mickey finds DiZ, revealed as Ansem the Wise, with a device to digitize some of Kingdom Hearts' power, but a system overload causes the machine to explode with Ansem consumed in the blast as the others arrive, with Riku restored to his original state.[65] At the top of the castle, Sora and his friends battle Xemnas, who uses the remnants of Kingdom Hearts to fight them.[66] Refusing to accept defeat, Xemnas separates Sora and Riku from the others to fight them in a final battle that ends with his demise. Though initially trapped on the other side, Sora and Riku are able to return to their world after reading a letter from Kairi that reveals the door to light.[67]
Sometime later, Sora, Riku and Kairi receive a message from King Mickey, the contents of which detail his findings in Kingdom Hearts coded: Sora is destined as the "Key that Connects Everything" to save Terra (whose body was taken by the rogue Keyblade Master, Xehanort, and became the newer incarnation of Xehanort that Sora faced in the forms of "Ansem" and Xemnas), Ventus (whose heart, damaged following a victorious struggle against his dark half, Vanitas, ended up within Sora while his comatose body is placed within the Chamber of Wakening), and Aqua. (who ended up trapped in the realm of darkness without any access to her Keyblade, and is with Ansem the Wise after the blast from the Kingdom Hearts Encoder brought him there). Sora tells Kairi that he must undertake another quest to save them, and she hands him her lucky charm again, telling him to give it back to her when he returns.