Sora received the message from the King nearly a year after Organisation XIII had been defeated. It was just about the time that Heartless had begun to be active again - and this was no mere coincidence. There had been a small detail that the keyblade bearers had overlooked when fighting nobodies in the last invasion of darkness - the soul.
Each person, Sora was told, is made up of three parts - a body, which gives them physical form, a heart, which aligns their reactions to the world, creating feelings, and their soul - an accumulation of all that the person was, is and will be. The soul was, in simple terms, their memories and true essence of being. It was also explained, that upon loss of a heart, the body and soul, if strong enough, can develop their own will and become beings know as nobodies - unable to feel, but still with their own intelligence due to their retention of a soul. When these nobodies were killed, it was always thought that the soul would be destroyed along with the body.
However, it was beginning to seem that this was not the case.

The sun had reached zenith and its rays beat down brightly on the calm shore, illuminating the soft sand and casting deep shadows beneath the numerous paopu trees dotted along the beach. Lapping waves and the occasional birdsong were the only sounds to be heard. All the evidence presented showed that it was just another, normal day on Destiny Islands.
Three friends sheltered from the sun underneath a tall coconut tree, huddled together in the small pool of shade from its large, outspread leaves. There were two boys - one older, with shocking silver hair and well toned muscles; a cool, collected kind of person, and one perhaps a few years younger, with long, ruffled brown hair and a still childish face. In personality, he was nearly the opposite to the older of the two - innocent and excitable but also quick to anger. Perhaps more likely to act before thinking. The other was a girl; cheerful like the younger boy, but quieter and a little more thoughtful. She was, in a way, a cross between the two boys.
Riku, the older boy, was the one holding the crumpled parchment. Sora ahead given it to him the moment that it had arrived, and all three had read it through several times.

Sora, Riku, Kairi.
I had hoped never to be forced to call upon you again, but the time has come that I am in need of your assistance once more. We had once assumed that when nobodies, a person's soul and body, were destroyed, the soul would ascend to the next life. However, this is not the case - unfortunately it seems that both the heart and soul is needed for this transition. These souls have become "lost", now looking for not only a heart but a host, too. This could prove exceptionally dangerous as the nobodies of Organisation XIII may not be as dead as we had hoped, and could be seeking vengeance as I write. Unfortunately, the fate of all the worlds once again is in your hands. I will be sending a gummy ship to pick you up and take you to Hollow Bastion in three days' time, where I shall give you more information. I hope you are all well in the meantime.
Regards,
King Mickey of Disney Castle

"So Organisation XIII could have returned?" Kairi asked, worried. She'd had run ins with the group of nobodies before, and none of them had been pleasant.
"I dunno. Anyway, it sounds serious. We should probably go pack," Sora said, taking the letter from Riku and rolling it back up.
"We've got three days," Riku said. "Kairi, you'd better stay here. It's not safe out there with heartless and these new lost souls as well,"
"No way!" Kairi argued, offended. "I'm coming with you!"
"Sure," Riku gave a wry smile. "You don't know what you're up against. The King needs people like me and Sora - we've fought before and we know what we're doing,"
"You're just scared that I'll be better than you!" Kairi punched him lightly on the shoulder. "My name was at the top of that letter too, and this time I'm coming whether you like it or not." She summoned her keyblade, a golden, flowery affair. "Sure, I might not have much experience, but I'm a quick learner, right?" She swung it around and the shiny metal glittered in the warm sunlight.
Riku still looked doubtful, but Sora chose to intervene.
"Riku, let her come. It can't be much fun waiting for us boys to come home from battling, not even knowing if we're all right or not, right, Kairi? How about I teach her some moves before we leave," He also summoned his keyblade, the Kingdom Key, and led Kairi off down the beach to where the two boys often trained. Riku sighed, following to watch. He took his time walking on the warm beach, feeling the sand beneath his bare feet. It had been too hot to wear his usual garments today, so he'd instead donned just a simple white sleeveless shirt and khaki three quarter lengths. By the time he'd reached the others, the illusion of serenity on this shoreline had all but been shattered. Kairi was blocking Sora's careful blows, and in the act, had pushed him back into the cool water. It splashed around his ankles as he dodged a blow from her and leapt forwards to attack again. Riku jumped up onto the old wooden jetty and watched them battle, Sora occasionally shouting instructions to his younger friend. The oldest of the group was reminded of when he and Sora had battled in the same carefree way, using old wooden swords made from driftwood. Of course, Riku had always claimed flawless victory, but that never stopped Sora from trying.
Eventually, a few minutes later, Kairi gave up, panting.
"C'mon, let's take a break now. I'm thirsty," She flopped down onto the sand, letting her keyblade dissipate with a flash. Sora nodded, also slightly out of breath. "Riku!" He called to the boy on the jetty. "Let's go get fruit juice!"
"Kairi given up already?" Riku teased, jumping down into the sea with a splash. Sora jumped away from the cold spray, so Riku splashed more at him. Of course, the brunette boy was unable to resist the change to get his own back, so he ran into the sea, covering Riku with water. Kairi eagerly joined in and soon they were all soaked to the skin. Sora sat down in the clear water, laughing. "What a way to cool off," He kicked his legs up and down, sending his own miniature waves off towards the shoreline. Kairi joined him, pulling a disgruntled Riku down with her. "Don't forget that in a couple of days we'll be fighting heartless again," Riku muttered, drawing his knees close. Neither Sora nor Kairi seemed as concerned as they should be.
"So we should make the most of the time we have left! Stop being such a pessimist, Riku," He whined, splashing the offender. "Come on, let's get drinks now. Training is really thirsty work,"

Kairi had a flask of tropical fruit juice in her bag, which she'd left under the tree, along with some healthy snacks. As she poured out the juice into three plastic beakers, Riku handed out the apples.
"Can't we have chocolate bars or something?" Sora grumbled, biting into his apple nonetheless. "Your mum is so annoying sometimes,"
"If you want that apple, don't complain," Kairi said, stealing the fruit from Sora's hands. The keyblade bearer made a grab for it, but Kairi held it out of the way.
"Fine, but can we have chocolate next time?" Sora submitted, and Kairi returned his apple, laughing. She also handed the two boys their juice and they all sat down next to the tree, sipping it thoughtfully. Behind them a small waterfall splashed down into a bubbling stream. "How do you fight a soul, anyway?" Sora wondered aloud. "I'm not sure," Riku replied. "It would be difficult to kill them if they don't have bodies,"
"Don't you boys ever think of anything other than fighting? What if the point is not to kill them?" Kairi objected. "Maybe we should be trying to reunite them with their hearts instead, so they can move on peacefully,"
"Their hearts were destroyed by the darkness," Riku replied.
"Nonsense! Hearts are made of light, they'll always be hidden somewhere in the darkness,"
There was a stunned silence. Evidently, neither Riku nor Sora had thought of this possibility.
"How do you know?" Riku eventually asked.
"Because... I don't know. But darkness can't destroy the light, right? It can only cover it. That means that no matter how dark it is, or how hopeless everything seems, there's always light, deep down, somewhere. You should know that, Riku. You were lost in the darkness and you still came out in the end,"
"But I didn't become a heartless or a nobody," Riku parried. "Things just don't work that way, Kairi. Sometimes the only way to help is by fighting,"
Kairi fell silent, angry. Sora began to think, however. Riku knew more about the darkness than anyone, but what Kairi was saying seemed to make sense. He was reluctant to say anything in her defence, however. He didn't want to upset Riku any more. Reunite all the souls with their hearts, no matter how far buried in the darkness they might be. That way they could go to the next life and no longer cause trouble in this world. That seemed to be the three keyblade bearer's task. "It seems really daunting, though," Kairi was saying, and Sora broke away from his chain of thoughts to listen. "If you think about all the nobodies that you fought, and there's a lost soul for each of them, that's a lot of hearts we'll need to find for them,"
"This isn't about finding hearts, Kairi," Riku mumbled. "But I see your point. They could be wreaking havoc in all the worlds by now."
"We'll just have to wait until we see the King," Sora said. "He might be able to find answers for us,"

They continued to talk until they had finished their drinks, and then Sora fought with Kairi some more. The girl had been right, she was a quick learner. Although she wasn't very strong, it didn't take long for her to pick up that she could overcome her disadvantage with her speed. With the abilities that Sora was teaching her, she was sure that she would be able to prove herself worthy of joining the boys on their newest mission.
As the sun dipped lower towards the horizon, the temperature also began to drop and Sora began to regret soaking himself in the sea earlier. "Should we go back now?" He asked, putting down his keyblade. "I'm getting cold," He noticed that Riku had put on his dry jacket and Kairi was now shivering despite the warmth.
"I want to watch the sunset," Kairi said. "Mum said the weather was going to take a turn for the worse tonight, so we might not get a chance for a while. But I'd like to go back and get some warm clothes,"
They all agreed. Particularly with such a intimidating task ahead of them, it was only fair that, just like Sora had said, they should make the most of the time they had left. They took the boat back to the main island and raced each other to get changed the quickest so they could return to their island. Kairi ran towards her house at the end of the long lane, where her foster family lived. She'd been found washed up on the shore of the very same island that she and her friends so often played on now when she was very young, and a kind family had agreed to take her in. She was always grateful for their love, and felt a little bad about leaving them like this. But on the other hand, she was excited about finally being able to fight along side the boys. For too long, she'd just been the damsel in distress.
She let herself in through the back door, and quickly ran up to her bedroom, thinking. Riku seemed so reluctant to let her come with them, but she knew it wasn't out of meanness, just worry. He well knew the effects that darkness could have on a heart and he didn't want Kairi to go through the same thing as he had. She reminded herself to tell him that she was one of the Princesses of Heart - so she couldn't fall into the darkness. She was annoyed that he didn't seem to accept her theory of light and darkness, and that the disagreement could cause a rift when they least needed it. It was a matter that needed to be addressed as quickly as possible, and hopefully the King would have the answer.
She grabbed the first dry clothes that she could find - a pair of loose beige trousers, a colourful sleeveless orange top that she couldn't remember where she got, and a white jumper with black trim as an afterthought. She also unloaded her bag and refilled it with a load of ice creams. She nearly tripped over the dog on the way back down, but managed to get out of the house in one piece. The boys were already waiting for her by the boats, so she apologised quickly and promised them ice cream when they got back to the island. Riku had changed into his usual dress - a sleeveless white and yellow jacket over a black body warmer and blue jeans. He was also this time wearing trainers. Sora was wearing similar trousers, and his old jacket, which was really getting too small for him now, but he didn't care.

They all climbed on top of the old paopu tree so they could watch the sun, now low in the sky, sink below the horizon. Kairi pulled the ice creams out of her bag before they could melt.
"That's odd," She said as she handed one to each of the boys. "There's one left over. I could have sworn I packed three. Oh well. Who wants the spare?"
"This is where it all started," Sora remembered, grinning as Kairi gave him the leftover ice cream. "It's weird to think that two years ago, we were sitting here, dreaming of going to other worlds, and now we've done it all."
"Not quite in the way I had hoped, though," Riku laughed. "And Kairi still hasn't seen all the worlds,"
"All the more reason for me to go," Kairi replied, elbowing Riku playfully. He glared at her, still not happy about her determination to join in with the quest. "Come on," She said, seeing his expression. "I can wield a keyblade for a reason, right? I promise I won't slow you guys down. Sora's been teaching me all the moves, I can hold my own,"
"I just don't feel like I should be putting you in danger. You're a girl after all," Riku grimaced and cowered as Kairi attempted to slap him.
"That doesn't make any difference!" She laughed anyway as Riku fell off the wide branch. Sora joined in with the mirth as he helped his best friend back up onto the tree. By now the sun had reached the horizon and the once clear blue sky was turning into a brilliant red and orange fire. A few clouds speckled the scene.
"You know why the sky goes red at sunset? Because red travels the furthest out of all the colours that make up the light," Sora said suddenly.
"How do you know that?" Riku asked. "What a weird thing to say,"
"I don't know," Sora admitted. "It just came to me,"
"Well, it's something I'll always remember now," Kairi said, gazing out towards the horizon. "It's so beautiful, isn't it? look how the light illuminates those clouds," She pulled out a camera and quickly snapped some photographs of the sunset. "Wait there, I'll take a picture of you two together, as well." She jumped off the tree and ran a little way away, before turning back and steadying the camera. There was a flash, and Kairi gave them a thumbs up. She ran back to show them the shots. "Riku, take one of me and Sora, and then Sora can take one of us," She gave the camera to him and got back up onto the branch. "That way, no matter where we are, we can always remember each other,"
It took a few minutes to take all the photographs and print them out. Kairi handed the one of her and Riku to Sora, her and Sora to Riku and kept the last one, of the two boys, to herself. "You're pretty good with a camera, Kairi," Sora said as he looked at the sunset pictures, back on the tree. Riku agreed with him, shuffling through to find his favourite. "Perhaps I should take it with me," Kairi suggested. "Then we can always remember all the places we've been and people we've met,"
"Yeah. It's so easy to forget what people look and sound like," Riku said as the last of the sun slipped into the sea, leaving just a sparkling glow on the horizon. Above them, the stars were starting to twinkle mysteriously. "Soon we'll be up there," Sora murmured, pointing to the pinpricks of light in the deep blue night. "We'll train again here tomorrow, right?" "I don't know, if the weather's not good-"
"You'll get wet," Riku interrupted. "If you can't take a little storm, you might want to stay at home after all," He teased. "No way! I can take anything you throw at me!" Kairi tried to push him off again, but this time he was expecting the attack and wrestled her back into her place. Suddenly, there was a flash, surprising the fighting pair. Sora grinned as he lowered the camera. "More memories," He held the camera out of reach, but Riku managed to pull it away from him, snapping a couple of Sora grinning like an idiot and a surprised looking Kairi. They battled together, trying to get good photos of the others without getting caught out themselves, just as the last slivers of light disappeared below the horizon.
Eventually they left the island when it became too dark to see, and said goodnight to each other, leaving for their own homes. At midnight, when all three were asleep in bed, the storm finally broke over Destiny Islands, covering the beaches and villages with rain. The once calm sea became a raging beast, tormenting the shoreline and rocking the boats perched helplessly on top of it. Thunder and lightning rolled angrily across the sky and darkness reigned.

Three days later, the gummy ship arrived to pick them up.