Crossover/fantasy/au: Demon slayer, Dark fantasy, Man vs himself

As one of the wind pillars, Kageyama was a serious guy with anger issues.

And also as a person that hangs out with Sanemi, he would really need some friends.

He did have friends, like Hinata that is a mist pillar, Yamaguchi as a water pillar, and Tsukishima as an insect pillar.

Though it was kind of hard for him to get along with them for their personalities are different.

Today, Tobio met a mew pillar that was a Sound pillar, (Y/n). He was much like Uzui, though he was a bit calmer.

Though, his confidence was somewhere like Uzui's

"(Y/n)!"

"Oh, hey Tobio!"

"Hey..uhm, where are you going?"

"On a mission"

"Oh, right!-"

Suddenly, red aura was seen in the air. Tobio's eyesight was great and because of that, he can see the aura. A demon's aura

"Why is there a demon here?.."

"There is? I would've smelled that earlier."

"...(Y/n), are y-"

"Kageyama! It's time for our mission! Come on!"

"..I have to go"

"Okay, be careful Tobio!"

"You too!"

On the mission of Kageyama, Yamaguchi and Hinata. All went well, except for the two arguing all the way to Kakunodatemachi (I just searched this town up)

The town was pretty old but the people that lived there were plenty.

The demon they were looking for was taking children and had to be stopped due to the grieving parents and grandparents.

The three of you all managed to defeat
Him in the end.

And as before you all went home, you guys bought some stuff and surprisingly, (Y/n) was in Kakunodatemachi.

"(Y/n)?"

"Oh! Tobio! You're here too. Have you defeated the demon?"

"Yes, we have"

"That's great! It was a lower rank, correct?"

"Yes, it was"

"It's surprisingly strong! I mean, you are all injured badly. Do you want me to help you guys back? I mean, I've defeated the demon in the town nearby"

"If you want to that is"

"I would gladly!"

"Thank goodness, I don't have to deal with these two alone. Thank you (Y/N)"

"No problem, my friend!"

You took Hinata that was fast asleep and Yamaguchi was carrying Kageyama who was currently limping, but the limping will eventually stop later on.

Getting back to their districts, they all rested. Not (Y/n) though, even after a long day of fighting a demon, he'd still train and train.

There was nobody that can stop him, otherwise it was about food he was being stopped for.

Like this one time Muichiro told him it was time to eat and Aoi prepared ramen. You ate a whole bowl which was added from all the other Hashira's bowls.(I'm hungry okay? ಥ⌣ಥ)

This night, everything was peaceful. (Y/n) was in the back where the other pillars train like Tanjiro and Yamaguchi.

Peace was broken when you heard someone behind you.

"Tobio?"

You look at him with wonder. He looked at you with fear in his eyes, and you do not know why

"What is it Tobio? Why do you look scared? Are you okay?"

"Don't come near me. I was only here to ask you a question, but your smell and aura explains it all"

"What do you mea-"

"Don't lie!"

You look at him shocked that he snapped at you. Could he already figured out?

"Do you.."

"You smell like a demon! And your aura shows one of a mercy less demon too!"

"...is that so? Well, you're the second person to know who I really am"

"Second?"

"Master Ubuyashiki knew, but he accepted me as one of his children."

"..why?"

"What?"

"You smell like a demon that has killed people. Why?!"

"...being a demon was the only way for me to survive"

"How?! How was it the only way to survive?!"

"Because, if I didn't become a demon, I would've been dead now"

"...then- then why did you kill people?!"

"In order for me to live. It was the only source of food for me at the time. But now, master Kagaya gives me a type of tea to prevent me from hunger for humans. But maybe there is another reason for why my aura seems like I've killed people before."

"What? Just tell me."

"Is maybe because I kill other demons mercilessly. I mean, they were once humans too"

"...I don't know why I trust you. But I will keep your secret"

"You will?"

"Yes.."

"...thank you, Tobio."

"Whatever. Get sleep, you'll be training Yamaguchi, Tanjiro, and Yachi tomorrow."

"Thank you, Tobio"

"You said that already. Now, I'll be going"

"mhm. Goodbye. Though, I never got to tell you that the moon looks lovely..infront of you who was the only thing I stared at.."

Unknowingly, Tobio was actually behind the door. Standing there in shock of the words. He then walked off and as he was far enough, he ran to his district, knowing that the person he now hates has feelings for him and may remain for so long.

(Y/n) never really wanted to become a demon. He became one for his family, and him to survive. Until now, his family still lives, though, they do not know a person that is named (Y/n) anymore.

He hated it. He hated how people ignored him, how he was neglected from the world. He hated himself.

Knowing there wont be any cure for being a demon after someone defeats Muzan. There are two people who will be able to cure him.

But for now, he'd have to stick with the horrid body he's been cursed with.