Demon Slayer AU

By: FunahoMisaki

(A/N: I own nothing and it was just a little blurb that hit me so I had to write it. Maybe a bit OOC.)

"I am truly sorry Tanjiro-kun. I never expected this to happen." Tamayo was bowing in apology the next night as they all got up and started moving about, her flawless skin now having a bite mark on the shoulder and neck junction that was already scarred over as if it were like a tattoo or an old wound.

"I know you didn't Tamayo-san and it's alright. I'm sorry that you are stuck with me now." Tanjiro said with a smile and an already scarred over bite mark on his own neck and shoulder.

To 'repay' her for her medical services, Tamayo had sent Yushiro and Nezuko to a different part of the house for them to gather supplies and all which had intentionally trapped them there once the sun rose. The part of the house they were in wasn't hit by the sunlight at all, but there was now a large hole in the living room that let sunlight in and they couldn't get around it.

The 'payment', as she had explained to Tanjiro, would be for him to help her through her heat. After all despite knowing of Yushiro's adoration of her, she saw him more like a son since she had turned him herself, and besides…for some reason it was worse on a female demon if another demon helped her through her heat. But normal humans couldn't survive it, normally because they got turned into a meal halfway through which made more problems than solved, and only Demon Slayers with their enhanced well trained bodies had a chance of surviving. The chances of finding a Demon Slayer who would be willing to help a female demon through their heat and not try to behead her however was next to impossible.

So Tamayo had spent more than four hundred years with no help at all with her heat and then this kind strong Slayer comes along and asks what he can do to repay her for not just bringing enemies to her doorstep but also for causing damage to her property and for bandaging up his wounds? Yes she had been embarrassed to have to ask this of the boy, especially considering he had agreed but mentioned that he was reluctant since they wouldn't be getting married.

Which had led to her telling him briefly about Demon Mates and how each Demon knew their mates were human and would or had been eventually born but most never found their mates and the few that did usually killed them by accident when they were human. The very rare few that had Demon Slayers for mates had either been killed by their mate who then slit their bellies or by other demons for being a 'traitor' to their kind.

He had agreed to become mates with her and she had explained that while it was a nice gesture it wasn't so easy. After all if just anyone could be a Demon Mate then it wouldn't be so rare would it? He had told her that when mating a Demon had to both bite their partner and be bitten by the partner on the neck and if they are meant to be mates then the bites would scar over and remain on their bodies no matter what.

Tamayo had fully expected the bite on her neck from Tanjiro to heal over in an instant and not scar at all. In fact she had told him that he could bite her if he wished to see if they would be Mates but she highly doubted that they were, and that if they weren't then while he had helped her through her heat then he could not marry her. Of course she also had to explain that if she ever met her Mate then they would surely understand why she had let another have her body so that was of no concern either.

Fortunately? Tanjiro had a habit of defying everyone's expectations and causing the impossible to be possible or come true. As evidenced by the Mate Marks that now adorned their necks.

"If anything I'm afraid you are stuck with me. Demons, the lucky few who do find their mates, mate for life. And the first time a demons mate dies, whether from age or disease or battle, the mate becomes a demon as well. It's the only way for any demon to create another." Tamayo explained and Tanjiro smiled softly at her and made sure she had plenty of time to pull away as he reached forward and grabbed her hand, pulling it up to his face and kissing her knuckles.

She blushed rather cutely as she stared at him surprised.

"I don't mind at all. It's perfectly fine with me. Besides…we're going to create a cure together right? So eventually we'll either both be demons for a while and then human again or we'll both be humans. Either way, there's nothing wrong." Tanjiro said and he gave her a bright smile that was filled with understanding and warmth.

Tamayo stared at him surprised for a moment and then she let herself smile softly.

"Yes…we're going to create a cure together." Tamayo said and her smile wasn't one of her easy long since perfected smiles, not this was a truly genuine smile.

"You should smile like that more often, it suits you." Tanjiro said grinning at her and she blushed a bit, her hand coming up to her mouth surprised and almost as if she was going to cover her mouth.

"You little-" Yushiro had arrived and either knew what they had been doing all day, or had discovered what it was as he stared at the marks on their necks.

"Yushiro-kun." Tamayo's stern voice stopped him in his tracks just before he could attack Tanjiro.

"It seems we will be sticking together now as you travel Tanjiro." Tamayo said and she kept her hand in his, squeezing his hand ever so slightly. His hands were rough and calloused but…they felt so warm and gentle in her own.

"Right. So we either travel together at night or we find some way to keep you both out of the sunlight during the day that I can carry if need be." Tanjiro said and he was trying to think of how to do so. After all they wouldn't fit in Nezuko's box even if they were in their small forms. Not all three of them and he was reluctant to have Yushiro alone in a box with his sister. Then again he was reluctant to leave any male alone with his sister.

Nezuko made a noise and when they looked over at her, she was pointing at a cart that had a roof on it and a door but no windows or holes to let sunlight in.

"Good idea Nezuko! They can ride in that and I can pull it along as we travel! It'd be harder to do on the roads and unworn paths out of the city but still possible!" Tanjiro said praising his little sister and giving her a head rub that she happily leaned into.

"That is possible and it lets us carry supplies with us for if anyone gets injured." Tamayo said smiling as well and looking briefly surprised when Nezuko appeared before her looking eager.

"She wants you to pat her head." Tanjiro said making Tamayo nod slowly and reach forward, gently patting Nezuko's head while she gave a happy noise and leaned into it. Much to Yuchiros jealousy.

"Nezuko…this is my mate, my wife. That makes her your new big sister doesn't it?" Tanjiro asked and Nezuko's big round eyes went even wider as she made excited and happy noises before she immediately wrapped her arms around Tamayo who looked surprised but smiled as she released Tanjiro's hand and hugged Nezuko back.

"We should get going before more demons come after us." Yushiro said glaring and sulking and hating the mark on Tanjiro's neck. It should be on his own neck not on that swordsmans!

"Good idea Yushiro-kun. Nezuko-chan do you want to ride in the carriage with us?" Tamayo asked smiling at the younger demon who tilted her head before she raced over to her box and climbed inside.

"I think you really like that box Nezuko-chan." Tanjiro chuckled and Tamayo shook her head slightly in disbelief before she left for a moment and returned with a pillow and blanket.

"Here. You could at least be more comfortable in there." Tamayo said and Nezuko made a happy purr like noise and nudged against Tamayo affectionately when the woman tucked the blanket in around her and placed the pillow behind her head.

"We can walk while it's night time and just keep the supplies in the cart. We should leave soon however." Tamayo said and Tanjiro smiled at her as he hooked Nezuko's basket onto his back and then immediately picked up the ends of the wagon and lifted it to carry everything that Yushiro was quickly putting inside.

"Ready?" Tanjiro asked and Tamayo and Yushiro nodded, Tamayo placing a hand over Tanjiros.

"Ready." No matter what came their way they were ready to face it together.

After all Tamayo hadn't found her mate in over 500 years and had never expected to find him but now that she had?

She wasn't letting him go.