Ever since he'd woken up without his fangs and appetite for human flesh, Tanjiro's life had felt like a dream; surreal and heavenly all at once. Sometimes he couldn't believe it was real, just too good to be true. Other times it felt all too real. Whenever he saw Urokodaki-sensei's or Tokito-san's shrines for instance. Somehow, he didn't think that equating negative with 'real' was something he should do, but he also hoped that passed in time.

Now was definitely one of those times when everything felt surreal. Tanjiro sat at a low table in a large room filled with bowls of food. Not a banquet, supposedly, but he couldn't really see a difference. Nezuko sat next to him, staring at the plates and bowls of food that were supposed to be more refreshments than an actual feast. From the look on her face, she couldn't see a difference either.

Around them sat many other Hashira and demon slayers. Actually, they made up most of the company in the room seeing as both the bride and groom had been Hashira. Tanjiro's eyes strayed to the happy couple seated at the head tables with their families (or, Mitsuri's family, apparently as nobody wanted Obanai's there… if any had survived). Mitsuri looked resplendent in her formal iro-uchikake* that had been dyed the traditional vibrant red on the bottom, with beautiful scenes dyed and sewn into it in gold. The red faded to a lovely pink that ended up matching her hair on top. He didn't know how they'd done her hair up like that, too. From what he understood, those types of hairstyles were usually wigs, but he doubted that anyone could really match her color of hair, so they must have somehow gotten her hair to stay like that. She smiled beautifully around at the guests, but more often at her husband dressed in the traditional black. Obanai himself looked a little stunned and overwhelmed, but happy. And Tanjiro was happy for them.

To be fair, it was a lot to take in. Honestly, the whole thing blew the time-traveler's mind. After all, he'd never expected to ever be invited to the nijikai** of a very wealthy family who offered all sorts of food and drink while encouraging everyone in the room to mingle, despite the obvious class difference between some of them. The only people on Tanjiro's side of the room who seemed to really know how to act were the Ubuyashiki children, unsurprising due to their station. They also were the only children under the age of thirteen there.

They sat next to Himejima-san who had tears running down his face… again, although only his size really made him stand out. Both Genya and Sanemi sat next to him, arguing loudly, and Uzui-san with his wives watched in amusement across from them. Next came the former Thunder cultivator sitting between Kaigaku and Zenitsu (as they'd proven they couldn't sit next to each other). Nezuko sat next to Zenitsu and Tanjiro next to her, of course. Kanao and Shinobu came next, and across from them sat Giyuu-san and Inosuke. He sat next to Senjuro, who looked a little traumatized, as he also sat next to his very boisterous brother, who sat next to Rengoku Sr, who seemed a little lost, but also happier than Tanjiro had ever seen him. Across from him, next to Shinobu, sat Akatsugi. He seemed to eye the food with both eagerness and melancholy as apparently the feast reminded him of some of the celebrations he'd participated in before his fiance had been killed.

From there, several regular corps members seemed just as thrilled and out-of-their depth (and some of them, next to Akatsugi, very scared). But it was an obvious celebration that everyone seemed determined to put their heart and soul into. Even people Tanjiro hadn't expected that from.

It was strange to watch Giyuu-san drink, actually. Much to everyone's surprise, he seemed like a happy drunk, smiling and laughing and talking and basically freaking everyone out. It was also nice. Just… surreal. And Tanjiro would never let him forget it, although he probably wouldn't have to bring it up himself as Shinobu also watched him, obviously amused.

Often, people would randomly get up to mingle and wait their turn to approach the bride and groom to wish them luck. Tanjiro hadn't been one of them yet, mainly because being around so many people without wanting to kill and/or eat them was… well, he needed to find another word for 'surreal'. He couldn't sense Akatsugi's emotions anymore, but he had no problem empathizing with how the former Waxing Third likely felt. It wasn't bad per se, but still difficult to wrap his mind around… and not everyone there would understand. On the other side of the room, several tables with people dressed in far fancier clothing and with much better posture all sat eating and drinking daintily. So Mitsuri's friends and family, most likely, other than those at the corps, of course. He could see them shooting the corps side of the room strange looks, and couldn't blame them.

Honestly, between the people and the volume, it was getting to be a little much, and Tanjiro really wanted to step out for a moment. Since people were supposed to mingle, he didn't think anyone would mind if he took a break.

"I'll be back," he said to Nezuko as he rose to his feet. She frowned worriedly up at him.

"Nii-san?"

"Just need some fresh air," he assured her with a smile. She didn't look entirely convinced, but still nodded. He made his way through the room, smiling at and greeting people as he pushed towards the exit as politely as he could.

Almost ten minutes later he let out a long, relieved breath as he stepped outside into the garden and the fading sunlight. It was just beginning to set over the horizon and Tanjiro watched it for a long time, breathing in his constant concentration to calm his body.

"Well, you're certainly a bold one," an unfamiliar voice had him jumping and reaching for the sword he didn't have. It was a wedding. In the Taisho era. Even the Shinazugawas hadn't brought swords. An older woman stood next to where he'd been just moments before, her eyes also fixed on the sunset. "Wearing your mark out in the open like that."

She was dressed in one of the finest kimonos Tanjiro had ever seen and had a sort of ethereal quality about her that reminded him of Waxing Moons, just… less violent. It still put him on edge.

"Mark?" he asked slowly.

She snorted (even that seemed elegant) and shot him an unimpressed look. "I'm guessing no one told you why most youkai wear masks of some kind? It's not just for traditional reasons, you know. It's rude to show your mark… and kind of stupid as it shows ally and enemy alike your power, fire boy."

Tanjiro just stared at her for several seconds. "Y-youkai?" he asked.

The woman's gaze turned on him and stayed there, pinning him down. "Are you new? What clan are you even from?"

He frowned. "The… Kamados," he answered truthfully, though something told him to not give this woman his full name.

She frowned. "Never heard of them. Where is their lair?"

Tanjiro was only growing more and more confused.

"Lair?"

More staring. "You can't be that new with that aura. Drop the act."

"I'm sorry," Tanjiro said slowly, genuinely apologetic, "but I honestly don't know what you're talking about."

They continued to stare at and study each other for what seemed like a very long time before the woman's eyes widened in recognition.

"You're one of those rare human cases, aren't you." She didn't say it like a question. "Oh, how fascinating."

She walked up to him, putting a hand on his chin and moving his head left and right, up and down, so as to get a good look at him. He wouldn't have let her if he'd sensed any amount of malicious intent, but he didn't. That didn't make him comfortable either.

"Fascinating," the woman said again as she stepped back. Funny, her robe didn't move how he thought it should, with gravity and friction and all. It seemed to move where she simply needed it to so she constantly looked regal and elegant. It set off more warning bells in his head.

"Then let me ask you this: do you have any ill intentions towards my granddaughter or her new husband?"

Honestly, it just felt like the shocks kept coming.

"G-granddaughter? You mean Mitsuri?" The woman's scowl deepened, but Tanjiro just decided to plow on anyway. "Of course not! I worked with her in the Demon Slayer Corps."

The woman's eyes narrowed and Tanjiro suddenly felt that hostile intent he'd been expecting earlier. "You're not a demon, are you?"

He winced. "No! Well… not anymore."

"Huh."

She didn't sound disbelieving like he'd expected her to. Was this how the rich acted all the time? The Ubuyashiki's hadn't. Honestly, Tanjiro felt so confused he didn't know what to do.

"What do you mean by 'not anymore'?"

He blinked again. Something about her tone… "You believe me? About demons?"

She sniffed as if she'd smelled something disgusting. "Those pathetic half-breeds? Failed experiments at best. Now you were one? I've never heard of a cure before."

"It's new," he found himself saying. "Developed to turn demons human again."

The woman blinked in surprise, then let out a laugh, although it sounded more incredulous than anything. "Maybe that experiment was more successful than anyone realized…" She seemed to draw in on herself and then her eyes flew open in realization. "Do not repeat that. To anyone else. Oh, we need to come up with a good cover story for this before you go over the border…"

"Wait… you're Mitsuri's grandmother…" Tanjiro said slowly. "And you're youkai."

The woman smirked. "I am." She reached up and put a hand on her face. Then she took it off. Her face. Tanjiro blinked and rubbed his eyes with his fists before looking again. In her place stood a large animal. A familiar animal dressed the same as the old woman had been. She also held a wooden mask in her hand painted to look like an old face. Oh.

"T-tanuki-san," he managed to croak out. Then he frowned. "I… thought tanuki were… um…"

"Male?" the woman asked dryly. "Of course not. We're a tribe of youkai. But women do often carry… pouches around and transform them into—"

"Okay, okay!" Tanjiro yelped and waved his hands in front of him, trying not to blush as the woman smirked playfully. Definitely a Tanuki.

"As amusing as you are, with your incredibly human reactions," her smile suddenly dropped, "you cannot begin to understand the danger your very existence has brought to this world."

Tanjiro spluttered at that a little. "Danger? But I'm not a demon progenitor anymore! We got rid of the demons!"

The tanuki blinked. "Progenitor?" she asked slowly.

The time traveler sighed. "It's a long story."

Even with her animalistic features, Tanjiro could read how utterly unimpressed she was at his answer.

Fine. "Well, it has to do with me being turned into a demon when we defeated Muzan the first time like wham! Boom! Ghaaah! But then he kind of poured all his demonic cells into me and was trying to control me from inside my head when I became a demon and when I woke up from that I woke the final form of my blood art, whoosh! Which sent me back in time to the morning of the day he attacked and tried to kill my family, and then every time I died after that it sent me back again and again but due to some things that happened I kept becoming more demonic even though I went back to being a human every time and my body remembered what it was like to change and so it kept doing so even when I was able to stop myself from becoming a demon this timeline, and because of that it sort of mutated and became stronger than Muzan's cells, which… yeah," he rubbed the back of his head sheepishly. "Didn't mean to but I guess my body just went, 'No!' and haaaaaa, and so I could turn people and his demons into my demons but I hated it because demon progenitor? Yuck. Blergh. So once we defeated Muzan, we came up with a cure, and thanks to that and my blood art, I was able to burn it out of me and the cure did the rest! And Tada!"

He grinned, hoping she'd followed that.

The tanuki stared at him, those golden eyes utterly blank. Then, finally, she let out a shaky breath.

"So you're the source of… Oh, this is worse than I thought."

"Why?" Tanjiro asked, utterly confused at his explanation only seeming to distress her more.

Taking a deep breath, the tanuki put her mask back on. Before his eyes, she melted into the old woman he'd seen before. Well.

"Demons were the result of an experiment. A thousand years ago, give or take a couple of decades, one of our healers wanted to see if he could turn humans into youkai. He… wasn't known for his kindness, even among youkai, and likely just wanted to either sew chaos or find a way to gain easily controllable youkai servants."

Tanjiro felt his jaw drop open a little as he began to put it together. "Muzan's doctor. The one he killed."

The now woman nodded. "No human should have been able to kill a youkai like that. No one expected it. We didn't find out about what had happened until the demons had become so entrenched into the human world that, according to our own rules, we could not interfere on a large scale. Rules that are in place for a very good reason, I might add.

"This is a very common cautionary tale from the world of youkai. It says we did try to help where we could; bestowed blessings, encouraged any half-youkai children to get involved… but little worked until a human woman and her husband began to search desperately for a way to save their child. She had been diagnosed with an incurable disease and was not expected to live to give birth. In her desperation, she came across a Kitsune who happened to be with child herself. Taking pity on the woman, the Kitsune blessed her that she would tie her life-force to the woman, and that would cause their births to mirror each other. If the Kitsune's child was born healthy, so too would the woman's. It would also extend the human's life. However the bond could only last for so long, and eventually the woman's sickness would catch up with her. She was warned she may only live long enough to see her children before she died, maybe a few years more if she was lucky.

"The woman accepted readily and thanked the Kitsune. Now, I am sure there was more to the deal than that," the tanuki rolled her eyes, still elegant and ethereal. Tanjiro wondered how she did that. "Kitsune aren't known to be terribly benevolent for a reason, but whatever price the woman actually paid, it worked. However, the Kitsune gave birth to two kits. Having so recently tied the woman's life to hers, even temporarily, caused the woman to bear twins as well."

"Yoriichi and Michikasu," Tanjiro almost gasped.

The tanuki woman paused, thoughtful. "I wouldn't know," she finally admitted. "Human names only mean something when given directly to a youkai, so we rarely remember them otherwise.

"In any case, the younger twin was born with youkai empowering him. He eventually left his household after his mother's death and began to teach watered down versions of youkai techniques to humans. I doubt he knew they were youkai, likely just natural to him, but many youkai were not happy with this development. However, they also hoped that it would give humans the edge they needed to destroy demons and decided not to intervene once again. It almost worked."

"But then the older brother, who had learned some of those techniques, joined Muzan, betraying his brother and all they worked for," Tanjiro said, feeling a little weak. This… this made so much more sense.

The woman looked surprised. "Oh, is that what happened? We couldn't always spy on that man and his demons, or those who fought them. But that does make sense.

"In any case, that did give humans the edge they needed to keep demons in check at least. And everything went on until recently, when many youkai who are sensitive to the flow of time became very sick. They claimed that time was resetting itself. I believe they counted 87 times before they claimed it stopped."

She paused, looking pointedly at the boy in front of her.

"I am so sorry!" Tanjiro said hurriedly, bowing low. "I did not mean to harm anyone! I didn't even know how it happened!"

The tanuki sighed and glanced up at the evening sky, now darker as the sun had just set. "Yes, yes. Well, strange things tend to happen when you meddle with time, intentionally or not." She returned her gaze to Tanjiro. "Such as you, for instance. You read as a youkai."

That took Tanjiro back and he just blinked at her for several seconds.

"For all intents and purposes, I believe you have become one. You even have a mark… although so does my granddaughter. I simply thought it was her youkai blood coming out though." The woman pulled a fan from her sleeve and tapped her lips with it thoughtfully.

"The… marks?" Tanjiro asked, touching the side of his face where he knew his flames stood out against his pale skin.

"Yes," the woman said. "The girl you came with reads as a half-youkai as well. Both of you should be fine when it comes to your marks. Normally they are too powerful for human bodies to bear for long."

So… the corps had been using youkai techniques taught to them by Yoriichi, and doing so could awaken or bestow yokai power on users… that… also made so much sense. He had to tell Shinobu-san!

"Is there a way to unmark someone?" he asked slowly, hopefully.

"A couple," she replied. "Look through some of the older tales. You should come up with ideas. There is more truth in them than you may realize."

Right. He could believe that now… even if he didn't want to.

"I have to go tell—"

"Please, you must be careful who you tell," the old woman interrupted, putting her hand on Tanjiro's arm. "If some youkai find out that this route even has a chance of working, or what those marks truly mean, it could spell war between our worlds. Some youkai would come and exploit humans, doing everything they could to turn them into their own slaves and servants, and I cannot say how many would succeed. It could only be a couple, or it could be hoards. Youkai tend to think of humans as a resource to exploit, not as living, breathing creatures who have their own choice, will, and power. I know humans, I lived among them for decades, and I know they will not take kindly to youkai exploitation. Also, if enough humans become yokai themselves, humans will have a way to fight youkai on their own terms, as I doubt they would be so weak as many youkai seem to take for granted. Can you see how this could destroy our worlds if not handled carefully?"

The former demon nodded slowly, knowing he'd gone pale.

"Now that humans have defeated demons," she went on, looking reassured, "we will likely pull back. We need to let that happen so something like demons does not happen again. "

Tanjiro gulped and glanced back at the door leading to the celebration party. "We cured several demons. Many of them have… traits left over from when they were demons. Those are also youkai marks, aren't they?"

The woman took her hand back and thought about his question for several seconds. "Likely, yes. But while I sensed an unusually high amount of youkai in there, I did not sense anything that would read as more than a distant descendant, with the exception of you and your… sister?"

He didn't answer. He'd heard too many stories about tanuki and their tricks. Thankfully, the woman didn't seem to be offended.

"In any case, you are here because you are close with my granddaughter, correct?"

Hesitantly, Tanjiro nodded, smiling sheepishly. "My mom kind of unofficially adopted her. We know she already has family, but that wouldn't stop my mom."

The woman raised an eyebrow, looking amused. "I see. Is she inside?"

"No. She had to watch my siblings, but Shinobu-san offered to go back to the Butterfly Estate early and watch the children so she could still attend later."

"Hmm. You should be more careful with names around youkai," the woman warned offhandedly.

Tanjiro gulped. Right. At least that hadn't been his name to give.

"As you are close to and have fought with and likely either saved or been saved by my granddaughter at some point, I will give you some advice and an offer. You may or may not age like a normal human, depending on how your youkai power develops. If you do not die, you will likely be requested to withdraw from the human world at some point. When that happens, you must not draw attention to yourself. Accept, follow, and then use a name that you have not used here to get around. Once there, find the tanuki and use my granddaughter's name to find me. I will help you establish a clan over there. I am doing this as much for my own safety and that of my family's as I am for yours. Understand?"

Again, Tanjiro nodded, trying to wrap his head around everything that had happened.

"You may be able to bring your sister, but you will not be able to bring any humans. And that is if you do not age and die like a normal human."

Not for the first time, Tanjiro really hoped he did. Still, this was an incredibly generous offer this woman was giving to him. He didn't think he could turn it down. "Yes ma'am. And thank you." He bowed again.

"Your politeness will likely get you places in that other world, but make sure you are not weak-willed. Living in the world of youkai is—"

They both paused as the former Sound Hashira slammed open the door behind them, startling both of them a little. He glanced their way and paled before turning and hurrying off around the side of the engawa.

"Wait a moment, Uzui-san!" a familiar and very falsely pleasant voice called after him. Not a moment later, his mother appeared in the door, smiling in a way that sent shivers down his spine.

"Kaa-san?" he asked.

"Ah, Tanjiro! Good to see you here. Your sister is looking for you. Please don't worry her."

He nodded hurriedly. "I was about to go back in."

"Good," she said. "Now, where did Uzui-san go? I still need a word with him."

The time traveler didn't even try to hide it. He pointed in the direction he'd seen the former Sound Pillar disappear.

"Thank you, dear," she sent an actual warm smile at him before the fake one returned and she began to walk after the man. "Uzui-san! You have yet to explain why you decided selling my 14-year-old daughter to the red-light district on an unsanctioned, unsupervised mission without my permission was a good idea! Can you please explain it to me?"

The two who had just been talking watched her until she disappeared with a step of her breath style. Her learning and using the Water Breath like that may have been the most terrifying thing he'd ever seen after Muzan's baby form.

"That was your mother?"

Tanjiro just nodded, not taking his eyes off of where his mother had disappeared from.

"And your name is Tanjiro?"

The Sun Breather shot her a dry look before smiling widely. "I never gave you my name." After all, if he did, she would have far too much power over him.

"True, true," she said with a grin. "I take it back. As long as you're vigilant, you'll be fine amongst youkai.

"Now, I would love to meet your sister. Would you mind introducing me to her?"

"Aren't you supposed to be dead?" he asked. "If Mitsuri sees you, she'll ask a lot of questions."

"Please, I have my own tricks up my sleeve." She took his arm. "Now, I believe this is the new way of escorting a lady, correct? Please, show me back to the party."

Tanjiro was a little uncomfortable, but also found himself amused at her antics. "This way then… er… what should I call you?"

The old woman just grinned sharply at him. "Mitsuri Senior, of course. It's not my name, but…"

He couldn't help it when he laughed and escorted her back inside.

END

xXx

AN: Because someone asked, basically Nezuko used her youkai abilities and was able to astral project with help from her father. :)

*Japanese wedding dress/kimono. Usually dyed red and gold, though there are often other colors on them. Depending on the material, these could cost upwards of the equivalent of tens of thousands of dollars on today's market.

** A nijikai is an after wedding party/mingling where people bring gifts, usually in envelopes as money for the bride and groom. Today these have become very modernized, but there were these types of parties in the Edo era too so…

Actually, finding anything on Taisho weddings is beyond difficult because it was such a time of change. Because Mitsuri comes from a wealthy family, I'm leaning towards a more traditional wedding with some Mitsuri changes here and there. Hence the wedding dress with pink towards the top (they're supposed to be red, the color of good luck, and red is still the official wedding color in other Asian countries to this day).

A traditional Japanese wedding today has 3 ceremonies – the official marriage before the gods at the Shinto temple, the dinner for family only, and the nijikai or after party. So that's what this is. :)

ALSO, as for what kind of youkai Tanjiro is… a sun spirit. They're kind of new. ;) Not Amaterasu, but they'd likely get to meet her at some point. Think of them as sun-flares or sun-beams personified.

I would like to thank Quathis, Found, TimeLordTim, and Kaylessa for all of their help in this. They were wonderful beta readers when they could help and I really appreciate it. I would also like to thank my Discord Community for their help with the odd poll or question I had, as well as any issues with the story and general feedback. And lastly, I'd like to thank all my readers for supporting this. It's in the top 10 most popular fanfictions for KNY on AO3 and I just really appreciate it.

Right now, I do plan on writing a couple more one-shots or related one-shots for what would have happened if Tanjiro hadn't won that last fight… but otherwise, this is finished! I posted the first chapter of this in May of 2021 and now I'm done I just…

Wow.

Didn't expect it to go that fast. O_o I mean, I did, because I expected it to be 20 chapters in the beginning (yes, we can all laugh at the fact that I thought this was going to be a fourth of what it ended up being) but this many chapters this fast? I feel I've learned a lot from this.

In any case, it's been a fun and wild ride and I've enjoyed so much of it. I do also plan on writing some of my own original stories and have sent some in. When they are published (whether by my own hand or by a publishing company) I will let everyone know here as it has been requested.

Please don't forget to fav and watch/kudos if you haven't already. Thank you all again!

Discord: discord. gg/xDDz3gqWfy (no spaces)