Birth By Sleep
Birth By sleep is the beginning of the lore in Kingdom hearts, it follows 3 main protaginists, Terra, Aqua and Ventus. This game mainly highlights the efforts of Master Xehanort, another keyblade master's efforts to create the X-blade (Ki blade) and unlock kingdom hearts for himself He does this by unlocking the darkness in Ventus's heart and creating Vanitas, a being made from ventus's darkness who's emotions embody the enemy found throughout the game, the Unversed. Throughout the game you see a build up of Terra falling into darkness and Ventus and Aqua being worried for him up to the point in the final fight, Xehanort uses the said darkness inside Terra to use him as his vessel, this results in Terra's mind being trapped in his armour, aqua lost in darkness trying to save him and Ventus in a deep coma from his fight with Vanitas, all though a small apart of Ventus finds his way into Sora
Taking place 10 years after Birth By Sleep, Kingdom Hearts follows 3 friends who live on an island Named Kairi, Riku and Sora. These friends find themselves wanting to leave their home island and their wish does come true but not in the way the had hoped. During a great storm, the island is consumed in darkness and the 3 are sent across the many worlds but not before Sora aquires the magically keyblade. During sora awakening in a strange new place, he meets Donald and Goofy, the famous disney characters everyone knows and loves and together they go searching for King Mickey and Sora's friends. As they travel through the worlds, sora learns more about his responibility as a keyblade weilder and also about the dark enemy known as the Heartless; yet the they do manage to find riku, it seems that he has teamed up with villans such as maleificient who's goal is to capture 7 pure hearted princesses and open kingdom hearts for herself, This leads sora and co traveling to Hollow Bastion, the residence of the heartless and maleficents evil plans and also the location of the missing kairi. When sora arrives he is confronted by Riku, who proves himself more worthy of the keyblade, resulting in Donald and Goofy going with Riku, but in the end Sora never gives up and regains the keyblade and defeats Riku. While Riku flees he is confronted by a man in a cloak telling him that to become more powerful he needs to give into the darkness, this results in another fight with Riku who turns out to be Ansem, seeker of darkness, a heartless that is in search of kingdom hearts. they ultimately battle and sora wins although he has to release his heart as it is then found that kairi's heart resides with sora, after sora releases his heart, he becomes a heartless but is called back into the light by kairi's powers. In the climatic ending of this game, Sora fights with ansem one last time but in the dark filled island of his home, he ends up beating Ansem and closing what is thought to be kingdom hearts but is actually the door to the realm of darkness with the help of Riku who had come to his senses and king mickey.