Titled The Story of Hikaru. This is part of the Homeworld Series of worlds, following Hikaru as he goes through his memories of his homeworld.
The scene before Hikaru as he stepped out of the door was one of immediate danger and terror. The world around him was unfamiliar and was in the process of being under siege by heartless. While he was unable to summon his keyblade, Hikaru still rushed to try and attempt to fight the heartless, but was stopped as he accidentally dripped over a dwarf, Doc. While Doc didn't recognize the boy, it took Hikaru a moment to realize that he was still going by Krowley when he had first met them, and thus had to reintroduce himself. Doc then told Hikaru to look after a small boy when he left to go for the boy's parents.
As Hikaru looked at the boy, not but six years of age, he realized that he looked strikingly similar to himself. When he asked the boy who he was, the boy simply stated that his name was Kurt. Hikaru, desperate to figure out who Kurt was started pestering him with question after question, but the boy fell silent as he resigned himself to his fate. As the darkness encroached upon the world, Hikaru passed out.
When next he awoke, there was a battalion of Keyblade Wielders, the SOS 25th Regiment, who had bested the darkness. As Hikaru started to pester the boy for more information, the SOS Members told him to back off, asking him for all kind of identification that the boy did not have and eventually incapacitated him.
When next Hikaru woke up, he was far flung into the future on a completely different world. There, he met the dwarf Happy, who told Hikaru about Kurt when asked. It seemed that Kurt was now a grown man and had just recently had a daughter. Trying to figure out who he was, Hikaru went to Kurt's house, only to find Kurt getting ready to go on a trip. When pressed for information, Kurt simply said that he was leaving his family behind as he had got distracted from his original mission. Find Kingdom Hearts and destroy the Darkness for good. With that, Hikaru blacked out again.
When he next woke up, he was back in his home world, The Iridescent Falls. There, Hikaru met with Sneezy, who after a brief reintroduction, the duo wandered about. Eventually happening upon his home, Hikaru spoke with his parents, joy filling his face. To the best of Hikaru's knowledge, he was about to leave home and train with Krowley to gain a keyblade for the next few years. However, as he talked with his parents more, he learned that it was not Krowley he was to meet with. Instead, it was his grandfather, Kurt. Stunned at the revelation, Hikaru's head was spinning and only got more confused, blacking out once again as his parents referred to him as "Aux."
When Hikaru next awoke, he was at Central Haven. There, he realized he was in a third person perspective as no one but Grumpy, the current dwarf accompanying him, could see or hear him. As he saw the former Order member, Rin, walking about, he followed after her wondering what she was doing. There, he saw her meeting up with an old and decrepit Kurt. While the two talked about Kurt's new assignment as head librarian, the topic of Aux had eventually come up. During the time they had been in Central Haven, Aux had grown into a much stronger and fully fledged keyblade wielder, that Rin had told Kurt to be proud of.
As she left, Aux entered, showing that Kurt didn't really have much respect for the boy, and told him that his only goal was to learn and master the keyblade. He eventually sent Aux away, telling him they couldn't trust anyone in Central Haven. As Aux went to go be by himself, unloved by his grandfather, Hikaru blacked out again.
When next he awoke, he was with sleepy, watching the scene play out before him again. He found himself in a strange lab that had a pod in it. Walking in, Kurt was dragging the now incapacitated body of Rin, meeting with a hooded figure known as Nequa. In the pod was the sleeping figure of Krowley. The two discussed the process of how they were going to transplant their hearts into the new bodies, thus completing each one's end of their bargain, and gaining their power back once again. With the transaction done, Nequa left, leaving Kurt now by himself. However, it was soon revealed that Aux had been watching the whole thing.
Horrified at his Grandfather's actions, Aux told the man he would report him. However, foreseeing this, Kurt had enlisted the aid of Misrabel, using her to steal the memories of Aux and leaving him an amnesiac. When Misrabel asked where she was supposed to place the memories, he directed her to a different pod, showing the sleeping figure of Hikaru. A replica made in Kurt's younger image, he instructed she put his memories there and give him the drive to become a hero. With that done, Hikaru passed out once again.
When Hikaru next awoke, he was in his memories of when he was first starting out in the Order. Merely an assistant at the time, the boy was simply hauling armor around before tripping and falling. It was there that he was aided by the familiar form of Kaida, who helped him pick himself back up. It was here that Hikaru played out the first moment that he had become friends with Kaida, happy to go through a memory that was his own, but eventually blacking out all the same.
When next he awoke, he was looking at his own comatose body, with his friend Aux towering above it. While Aux was grieving for his lost friend, he was approached by Nequa. Not knowing who she was, Aux listened to her as she told him of a way to save Hikaru. Being a broken replica, unable to be sustained by just memories alone, she told Aux that using this device known as a "Remnant," it would save Hikaru. The Remnant would force the light out of Aux and into Hikaru, causing only darkness to exist within his heart. Without a second thought, Aux used the remnant, thus bringing Hikaru back to life.
When next Hikaru awoke, he was in his own Station of Awakening. Facing off against the Remnant, he came to understand who he was and what he was to do. Not wanting to be bound by the path Krowley had laid out for him, Hikaru found his resolve to protect his friends and live his own life from here. With that, he summoned his keyblade back once again, and defeated the Remnant, the world around him fading as the illusion ended.