On AO3 you can do this clever little thing that creates a link from your story to any story set as 'inspired by'. I didn't realize until a day or two after uploading that I gave Fanficiton dot net ThatOnePsycho's username, but not the name of the exact story that was my inspiration. The name of that story is 'Fears and Lies Melt Away'
The dining room of the Xiao Long household was uncomfortably quiet. Kairi had just spent the better part of two hours explaining several things to Taiyang, things the man would need to know if Kairi had any hope of following through on her intentions. He obviously had many questions, and Kairi did her best to answer them patiently.
"So… you're not really a huntress?" He finally asked at the end.
Kairi raised an eyebrow. "That's your takeaway?"
Taiyang dropped his head into his hands. "It's the only thing I can… comprehend right now. You really expect me to believe in magic, in other worlds, and that my Ruby is now in line to inherit some ancient power? What even is a 'Keyblade'?"
To answer that, Kairi summoned her own. The flash of light made Taiyang jump, and he stared at the weapon with both shock and awe. "So… maybe I'm a little more receptive to this 'magic' business…"
Kairi dispelled her Keyblade before continuing, "The fact is, there is a chance Ruby is already set to inherit the power of the Keyblade. If she does, she'll need the right training. Training no one on Remnant can give her."
"How much of a chance?" Taiyang asked.
"I wish I knew," Kairi confessed, "It would make this conversation so much easier."
Taiyang groaned as he processed. "She wants to be huntress, and I don't believe that dream will die with age."
"Is this so different than sending her to one of your combat schools?" Kairi pointed out, "She'll be training to fight, to use her special abilities, and to use those skills to protect people. It will just be on a… much larger scale."
"Sending her to Beacon is a little different than sending her to another world entirely," Taiyang laid out his counter-point. "How would I even visit this 'Land of Departure'?"
This was the question Kairi feared most. "You… couldn't."
"Excuse me!?" Taiyang started to raise his voice.
"It's the World Order," Kairi told him. She had explained the concept earlier, and Taiyang groaned again. "Technically, I shouldn't be telling you any of this. The only reason I am-"
"Is because of Ruby," Taiyang cut her off, his voice quieter, if not quite calmer.
"I promise, I have no intention of separating your family," Kairi assured him, "I'm sure the other Masters and I can agree to some kind of visitation where she can stay here for a time on a regular basis."
Taiyang stroked his chin stubble, thinking deeply. "Okay. Say I even believe any of this. What if I say yes, and she doesn't get a 'Keyblade'?"
"Then there won't be anything we can teach her," Kairi explained, "There is a ritual I could perform to make sure she gets a Keyblade before I leave today-"
"Today!?" Taiyang started to shout again. "You would leave with her today!?"
"N-no!" Kairi quickly recovered, "Even if I do the ritual, she won't get the Keyblade right away!"
"So what your saying is that if I agree, you will take Ruby to train her if she gets this 'Keyblade'," Taiyang put his thoughts together, "and if I say no, she might get a Keyblade anyway and then be carrying a power she doesn't know how to use?"
"That… is the heart of it, yes," Kairi nodded slowly.
"This..." Taiyang sighed, "This is just too big. Even if I believed you, I can't decide my daughter's future for her like this..."
"I understand," Kairi nodded, taking it as a rejection.
But if it is all true… "Can you bring proof?" He asked.
Kairi paused. "I-I'm sure the other masters and I can come up with something," she told him, her hopes rising again.
"Bring proof, and then we'll talk," Taiyang laid down the law.
It was enough for Kairi, who smiled and nodded.
The Land of Departure was a brilliant place. Marble halls gilded with gold, it was a fantastic sight to see. Perhaps even more impressive than the sights was the people. The highest concentration of Keyblade wielders for a generation met in these halls, and two among them were engaged in an important conversation.
"Do you think I did the right thing?" Kairi asked Aqua.
"It is a difficult call..." Aqua noted, "We still don't know everything about Keyblades, and I doubt we ever will. It is kind of a living weapon, after all. If your heart is telling you she'll get one because you Linked with her heart, then I don't see a reason to argue otherwise."
"It is rare to Link with someone so young..." Kairi nodded. "Princesses of Light, other Keyblade wielders, and world inhabitants who already have their own strength and skills are one thing. But a five-year-old with nothing but a strange amount of magic power, especially in a world with no natural magic?"
Ventus, who had been listening in nearby, finally decided to speak up. "Well, I think you did the right thing!" he called out cheerfully, "and if this 'Ruby' is half the girl you described, she'll want this! No questions asked!"
"We'll know in a few days," Aqua concluded for all of them. "Until then, I do believe congratulations are in order, Master Kairi."
"Oh yeah!" Ventus picked up excitedly, "this 'Ruby' girl aside, you completed your mission! You totally passed the Mark of Mastery!"
Kairi found herself smiling at the new title. "Thank you, Master Aqua."
"You can still just call me Aqua, Kairi," the older Master reminded the new Master.
"Of course. I just… y'know..." Kairi smiled.
"Trust me, I do," Aqua smiled in turn.
"And so will I! Someday..." Ventus chirped.
The two girls gave Ventus a strange look, and all three soon began laughing.
Once the laughter had died down, Kairi still had one last question. "We still need to prove to Ruby's father that other worlds exist."
Aqua thought on that for a moment. "Considering we want to take his daughter for training, I believe we can make an exception to the World Order, just this once. I just need to borrow something from King Mickey."
After a few days to clear his head and process, Taiyang was wondering how he could ever start to believe that Kairi girl's nonsense. It's not like I haven't seen my share of strange things, he conceded. And there was just… something about her. Something trustworthy. Like my heart wanted to believe her.
In the end, he did indeed inform Ruby of what Kairi said, though he made it clear the woman could also have been simply crazy. Ruby, however, seemed to believe in an instant, regardless of Taiyang's warnings.
"Look, if she brings proof of other worlds, and that's a big 'if', then we'll consider this," Taiyang told his youngest, "But you really need to understand how big this decision is. Your entire life could change in ways you can't take back."
"But I'd be helping people, right?" Ruby asked.
"You can help people as a huntress," Taiyang pointed out.
"Yeah," Ruby nodded, "But if I go with Kairi, I could help way more people, right!? On a bunch o' worlds!"
Taiyang sighed. He didn't want to take this choice away from Ruby if it was all true, but he would be lying if he said he didn't hate the idea Ruby was so into this. "If she's even telling the truth, which she probably isn't. I mean, this is all way to crazy. I can't believe I listened to her at all..."
Ruby held her hand over her chest. She could feel something inside of her, a pulsing warmth that reminded her of Kairi. "She'll be here. I believe in her."
That conversation happened a few days ago, and Taiyang had been unsuccessful since in convincing Ruby that Kairi might be lying, and even less successful convincing her to say no even if Kairi was honest. Taiyang found himself hoping Kairi was truly crazy and would never return, and had a difficult time entertaining the thought that the girl would bring some irrefutable evidence of her truthfulness.0
With such disbelief in his heart, he was truly surprised when she house began shaking, accompanied by a sound resembling a high powered airship engine outside. He stepped outside and could only stare at what he saw. A large, mutli-colored airship hovering above his front yard. A flash came from the undercarriage, and out of the light stepped Kairi and another girl, this one dressed in simple blues and blacks with shingled armor on her forearms. The new girl's hair and eyes were both blue as well.
"My name is Master Aqua," the blue girl introduced herself to Taiyang.
"So..." Taiyang tore his gaze away from the craft, "you're another Keyblade Master?"
"That is correct," Aqua nodded, "and you are Taiyang Xiao Long, I assume?"
"Right..." Taiyang was getting distracted by the colorful ship once again. He quickly shook himself back to his senses. "Perhaps we should take this inside..."
The three entered the house, and Ruby came tearing out of the hallway. "Kairi!" she hugged the wielder's leg as she ran into her.
"Good to see you again, Ruby," Kairi smiled.
"So this is the little one?" Aqua knelt down to Ruby's eye level. "Hello. I'm Aqua, a fellow Keyblade Master."
"You have one too!?" Ruby's eyes shone, "Can I see it!?"
"Calm down, Rubes," Taiyang interrupted. "We have things to discuss first."
"Maybe later," Aqua promised. Soon, everyone in the house gathered in the dining area. Taiyang wasn't sure about letting his daughters sit in, but did so at Aqua's insistance.
"So..." Taiyang scratched his chin, "That airship outside is impressive, but it doesn't prove other worlds. Why didn't Kairi have it last time?"
"Keyblade wielders have their own way of traveling the worlds," Aqua answered, "She didn't have the Gummiship last time because she didn't need it."
"So why is it, the Gummiship you said? Why is it here now?" Taiyang continued.
"You want proof of other worlds," Kairi piped in, "What better proof than seeing it for yourself?"
Taiyang's eyes widened. "What about the 'World Order'?"
Aqua answered for him this time. "We've decided, given the situation, that we can bend the rules a little. Just this once. It will allow the three of you to see another world for yourself, see where Ruby will be training if you agree. You will also get to meet the other Masters that will be teaching her for yourself. And if you don't like what you see, you still have the option to refuse us after the trip."
"Three of us?" Taiyang asked.
"Yourself, Ruby, and your other daughter," Aqua answered. "We won't ask you to lie to her. Even if I wanted to, I imagine it would be very difficult. As her sister, her family, she deserves to know what's going on with Ruby as much as you do."
"If you agree in the end, of course," Kairi quickly interjected, trying to keep Taiyang from feeling pressured.
"We get to see another world today!?" Ruby cried excitedly.
"Wait," Yang scratched her head, "does this all have to do with that stuff you've been talking to Ruby about?"
Things were getting crazier and crazier. Finally, Taiyang considered the possibility that this was all too crazy to be a lie. Who could make this crap up? "So. The Land of Departure, right?"
"Right," Aqua nodded, "However, there is one more thing. You don't have to commit Ruby to us yet to see the Land of Departure, but there is something else you must commit to."
"The 'World Order'?" Taiyang astutely deduced.
"Right," Aqua confirmed, "you can't tell anyone about what you see today, nor can you tell anyone what Kairi has told you previously. And neither can Yang or Ruby. No matter how close someone is, or how much you trust them, you must keep the secret."
"We can't tell anyone…?" Ruby said quietly. That was one rule she wasn't expecting.
"The World Order is the most important law for world travelers such as us Keyblade wielders," Kairi added to emphasize the point.
Taiyang rubbed the back of his head. "Well, the girls have a close uncle. He doesn't live with us, but he stops by regularly. What do I tell him about Ruby vanishing for months at a time?"
Aqua frowned, "I'm sorry, but I don't know. Not that I don't want to help, but I don't know enough about this world to invent a viable excuse."
"I can't tell just him?" Taiyang argued.
"I'm sorry, but a line has to drawn. If not here, then where does it end?" Aqua counter-argued. "You and your other daughter are Ruby's immediate family who actually live with her. Anyone more than that, cannot know."
"We'll help bounce ideas to create a story for Ruby's absence, if she does come to train with us," Kairi offered. "If she doesn't, then you don't have to worry about telling their uncle anything anyways."
"So I can't tell Uncle Qrow either…?" Ruby asked quietly.
Kairi moved to sit next to Ruby. "Imagine you had a weapon, a powerful one you could use to do so much good. But, you also knew that evil people could easily take advantage of that same weapon for their evil deeds."
"Most people across the worlds couldn't leave their own world even if they knew," Aqua explained, "But some people could. Through science, dedication, or by embracing dark powers. The more people that know, the higher likelihood that someone malevolent learns. And then everyone is in trouble."
Kairi looked down into her hands. "The last time someone evil discovered worlds outside their own, she kidnapped me right off my home world, as well as six others from theirs, to try and use us to open a door to the ultimate light and take over all worlds. None of the seven even knew of worlds outside their own before then. Even then, Maleficent's plan was hardly the worst plot we've had to put a stop to."
"So that's what I'd be doing," Ruby looked up to Kairi. "Protecting not just Remnant, but all worlds. Everyone." The little girl's resolved steeled over once again. "I wanna do it, dad!"
"All of this conversation is pointless if other worlds don't actually exist," Taiyang reminded her daughters. "Let's see this Land of Departure first before we do anything drastic."
"Then," Aqua stood, "I don't believe there is any reason to delay."
Taiyang readied his girls, locked up the house, and boarded the Gummiship with his family and the Keyblade Masters. The last bit of Taiyang's skepticism vanished as the Gummiship successfully left Remnant's atmosphere. Aqua raised her Keyblade to open a portal and they passed through it into a beautiful realm right out of a space movie.
"Welcome," Aqua offered, "to the Ocean Between."
"Woah..." Ruby stared out the window at the sea of stars.
"It will be a little while before we reach the Land of Departure by Gummiship," Kairi explained from the driver's seat.
Taiyang and his daughters were enraptured by the sight outside the glass. Aqua got Ruby's attention and ushered the girl to her side. She knelt beside her and pointed out the window. "Every single one of those stars is another world. As Keyblade wielders, it's our responsibility to protect all of them."
"All of them?" Ruby breathed in awe. "There are so many? How do you protect all of them?"
"It's not an easy task," Aqua confessed. "Even if one dedicated themselves to travel, and only spent a few minutes in each world, I doubt even a fraction of them could be visited in a single lifetime."
"But that's no excuse to slack off," Kairi spoke up. "One person may not be able to do much. But, if everyone does their part, peace would be far from a dream."
Ruby was not the only one soaking this information in. Yang stared at her sister and the people surrounding her, conflicting feelings swirling behind her eyes.