This is something that nobody has ever done in the website and I think is a big opportunity. Now you might be thinking ´´Aren't Devils and Demons the same thing?´´. No, I will go in detail on how they are different, also this is a case of different universes with a hint of magic. This will be explained down the line.

Also, in my continue list of ´´Put more interesting characters alongside Issei´´ we have Tanjiro here. We have one of the sweetest, gentil, hardworking and overall great Shonen characters over the last few years. Plus, it would be funny see someone pure like him have to deal with girls wanting to sleep with him. Before you ask NO! Nezuko won't be part of his harem! This twisted and sick! She won't appear for a while in the main story, if you ask me Nezuko is the little sister that doesn't want her big brother get hurt with all this new found attention. Well lets get this show on the road. This takes place after season 1 so all the Hashira are alive.

At the Butterfly Mansion

The young and prodigy demon Slayer Tanjiro Kamado was ready to start a new day of training. Ever since him, Nezuko, Zenitsu and Inosuke were accepted to stay at the Ubuyashiki region he has improving his skills on a daily bases. Mostly thanks to the help of others demons slayers.

''Ok, time to go.'' Said Tanjiro with his sword and uniform ready.

''Mister Tanjiro, what would be doing today?'' Asked one of the youngest member of the mansion Kiyo.

''I will be at the river down at the forest. I want to see how long I can endure the pressure of the water.'' Said Tanjiro, saying the last training mission send by Shinobu.

''Be safe.'' Said Kiyo

''And don't get sick.'' Said Naho

''Also don't forget to eat.'' Said Sumi.

''I won't, thank you all.'' Said Tanjiro grabbing some snacks for later.

Before he could go he stared at the box where his sister was currently inn. Nezuko was sleeping at the moment since it was the day.

''nezuko please stay here. Its morning and I don't want you to get hurt.'' Said Tanjiro putting a hand on the box.

Before he left he saw four new figures coming. Aoi, Kanao, Inosuke and Zenitsu. All of them his friends that learned to live with his demon sister.

''We will take care of your sister.'' Said Aoi as Kanao nod.

''Once she gets out, she is fighting me!'' Scream Inosuke.

''Nezuko-chan is too much of a flower to fight a ugly beast like you!'' Scream Zenitsu.

Tanjiro just laugh at that. After the hell he has been through the last two years, it was good now to have some light at the end.

''Thank you all.'' Said him

As he was about to leave Aoi felt she forgot to tell him something and runs off to speak.

''Tanjiro-kun wait!'' Said her.

''What is it Aoi?" Asked him

''The master wanted me to inform you that you should stay around the water for around two hours. He wants to see if your endurance has improved.' Said Aoi.

''Alright, thank you for informing me.'' Said Tanjiro

''Alright.'' Said Aoi

The teen nodded that and left towards the river.

Tanjiro has done a lot of training over the past few months. If it wasn't for Urokodaki and his ridiculous training he would have been broken already, but he learned to endure the pain and do what it could in order to become a good demon slayer.

At the River

This River was one of the few near the Ubuyashiki region. Apparently the others were near a place called ´´The Swordsmanship Village´´ a place that Tanjiro need it to see later. This place had a clear view, almost glass like water reflecting his image and it was a great sight. There was also a Waterfall, not big but enough to have a great amount of water splashing all around.

''This river has an almost mystical atmosphere. I haven't felt something like this since I did the Final Selection.'' Thought him.

He then took off his shirt and went towards the water.

''Ok two hours.'' Thought him.

The teen stay under the waterfall, all that water splashing him and he was doing his best to not feel like this was hurting him. He need it to sense the water and feel like him and the element were one.

''Why do I feel a weird sensation around this place?'' Thought him.

As Tanjiro kept training under the waterfall he heard something. A voice, an almost childlike voice in this surrounds.

''Come…'' Said the voice.

''Huh?" Asked Tanjiro.

''Come Tanjiro…come to a new world…'' Said the voice.

The teen soon got out of the water fall and took off his katana.

''Who is here?" Asked him ready to fight.

He then took a smell of the air to make sure there was someone there, however no such luck.

''No smell.'' Said him in wonder.

He kept his sword in handy in case something happened. He wasn't going to let his guard down.

''Come…to a new world.'' Said voice.

Tanjiro didn't like any of this. He wanted to make sure there was no demon nearby before he go and ask for help, however that wasn't the case.

At the main mansion.

Ubuyashiki was looking at the beautiful sunny day. He was just sitting on the balcony with his wife and children.

''Dear why are you smiling?" Asked his wife Amane.

''I made a decision that can really help us in the future. A challenge that can change the formation and idea of the Demon Slaying corp.'' Said Kagaya.

''So do you think one of our current slayers is up for this said challenge?'' Asked her.

''yes, if we want to defeat Muzan we need to try out all the options that are given to us. Even if its sounds a bit difficult.'' Said him.

''Why do you say that?'' Asked her

''That River near the butterfly mansion…it can act as a gate on certain occasion and today it opens. I send a certain person to go there and participate of this challenge.'' Said Kagaya.

Amane didn't know what he was saying. Yes, she felt that the river was rather unusual, but the fact that someone was going to face off the weird challenge that her husband was setting on gave her a rather nervous looks. She then remember who was send to be in that river.

''Tanjiro.'' Said her.

''He will be fine. If something goes wrong, I will send a hashira to rescue him. Trust me Amane, this will be for a better future.'' Said Kagaya holding his wife hand.

The woman looked at her husband and never once distrusted him, she knew if there was someone that could overcome the impossible was the child that managed to travel with a demon and keep her in check.

''I believe in you.'' Said her holding her husband hand.

Back with Tanjiro.

The teen looked around in confusion. He felt that something was going to happen, and he need it to be ready for what was about to come.

'What is going on?" Asked him.

Tanjiro then noticed something, the water of the river was bubbling, but it wasn't getting hotter. The temperature was normal and nothing different.

''Huh the water is the same. What is going on?" Thought him in wonder

Soon the bubbling started to get more and more violent. It was like a little earthquake was happening.

''Wow this is surreal, but what it is?" Asked him.

''Tanjiro…'' Said the voice.

Tanjiro got distracted by the voice that he ended up losing his balance and falling down on the river.

''Aaaah!'' Said him being dragged to the bottom.

The water was shaking too much and the small river felt like a powerful and stormy sea. Tanjiro kept trying to swim back but it wasn't working.

''I can't stay here…I need to get back…to Nezuko.'' Said him.

However it was too late, the river felt like a sense of pulling and dragged Tanjiro to the bottom to which he disappeared.

''AAAAAAAH!'' Said Tanjiro being taken away from his world.

There were a few places in the world that can take someone to another form of reality. This was one of them, the tricky part was that nobody knew where the other reality could be. It could be a pleasant one or a nightmarish one.

At Kuoh

The little lake that was cited in the park of the town started to bubble up. There wasn't a person around to see what was going on. Soon it felt like something popped out of the water.

Boom

Tanjiro emerged from the lake pretty much panting, almost like he almost drown.

''Huff Huff Cough Cough.''

Tanjiro looked around to take a deep breath and make sure that everything was still with him. His uniform, his earrings and his swords were all there. However, he looked around and saw this wasn't the same forest that he was once was.

''Huh?" Asked him.

He got up and started to look around, making sure he was in the same place. However, upon seeing more of the park it was clear that this wasn't the region that he was with his friends and sister.

''Where am I ?'' Asked him.

He started to look around nervous. Thinking that the river might have dragged him to another region, one far away from the Demon Slayer Headquarters.

''What is going on?" Asked him nervous.

At Kuoh Academy.

In a School Club Room

The club had only two people present. One woman with beautiful red hair, slim body and big breast size. The one other has black hair, ribbon making into a ponytail, slim body and also big breasts.

''Akeno!'' Said the red haired girl named Rias.

''What is it Bunchou?" Asked the black haired girl named Akeno.

''Do you feel this weird energy?" Asked Rias.

''Weird energy?'' Asked Akeno.

''Concentrate.'' Said Rias to her friend and soon she felt it too.

''Yes, I can sense it.'' Said her.

''This is not some normal energy. Its something more.'' Said Rias.

''Where its coming from?" Asked Akeno

''I think it's coming from Kuoh town park.'' Said Rias looking at the window.

''So what do we do? Do we check the park?'' Asked Akeno

''of course, I am curious about this energy.'' Said Rias.

Back at the park.

Tanjiro got all his stuff and started to walk around in the park. He was hoping to find someone to let him know where he was and how to get back at Headquarters

''Someone, please anyone would be good.'' Thought Tanjiro desperate.

Then Tanjiro sees someone. He was a bit weird for his eyes, but at least was another person.

''Oh good! A person!'' Said Tanjiro with hope.

Tanjiro then approaches the man. He was wearing a closed suit, what looked like a big coat and some weird hat.

''Excuse me sir, I am lost can you tell me where I am?" Asked Tanjiro but the man wasn't that nice of person, or even a person.

''I thought I felt a strong energy coming from this park. I though it was a monster but it was just a kid.'' Said the named that was called Dohnassek. He hoped to find something interesting to fight, but instead he found this weird human boy with a green Kimono, earrings and a katana.

''Uh?''' Asked Tanjiro confused.

Dohnaseek then turns to Tanjiro with a smirk in his face.

''What is he doing?'' Thought Tanjiro.

''Kid, tell me something? Do you believe in the Fallen Angels?" Asked him.

''Fallen Angels? The ones from the bible? Sorry, but I am a follower of Shinto.'' Said Tanjiro.

The man just started to laugh at that. A follower of Shinto, he thought they were all gone but it appears there was still some still around.

''I don't know what you are but I can tell you are no ordinary human.'' Said Dohnaseek.

''What?" Asked Tanjir.

''You look interesting, I will show you what a fallen angel can do.'' Said him and then two large wings like a crow appeared behind him.

Tanjiro saw that and soon got his Katana ready for action. He knew it was against the Demon Slaying Corp rules to fight against other things besides a demon, but this man wasn't human at all.

''I don't know if he is a demon or not, but his smell isn't a pleasant one. I need to be careful and then figure out where I am.'' Thought him.

The demon slayer boy was now getting ready for combat. Not even 5 minutes into this new place and he was going to fight a new enemy.

Ok, this is overall really good. Tanjiro is the new world thanks to mystic river that Ubuyashiki new. He wants Tanjiro to find allies to help them in their quest to fight Muzan. But also don't think that the corps are the only ones that have something that can go to other worlds, let me just say that some demons might popped out against the devils. This will be interesting and let's see how things will go.

Also, Tanjiro will be with the second years. I know he is a bit younger, but hey its my story and I can do what I please. He won't register to school yet. See you all next time.