The Multiverse Voyager

Hello everyone, before we start I would like to clarify this story will be posted on both Wattpad and Fanfiction

"Person speaking"

"Person thinking"

"Other Entity speech"

"Other Entity thoughts"

"Attacks"

If you read on sites without Bold, Italic, or Underline available

"Person/Entity speaking"

'Person/Entity thinking'

[{Chapter Start}]

Tanjiro Kamado, the main character of Demon Slayer and the one who would have killed Muzan if I was not in this world. While I would normally be excited to meet someone like him, this news only made my eyebrows furrow in contemplation.

According to Urokodaki-Sensei, the final selection happens once every two years. From what I remember, Tanjiro trained for two years before attending the final selection. Or was the final selection once every year and not 2? Ugh, I don't remember these details.

Let's assume the worst-case scenario and say it happens every 2 years. Assuming that, I have a very limited amount of time to participate in this year's selection. While I wouldn't mind training for a longer amount of time, I'd rather be done with this world quickly.

"Sensei, How long is it till the next final selection?"

"About a month"

1 month isn't enough time for me to become strong enough to survive in the final selections. Even if I do survive, I'd be a demon slayer with incomplete slayer training, and that's only going to be harmful to me in the long run.

I jolted, feeling a hand on my shoulder, my hand instinctively went to my katana, only to find it not there. I relaxed a bit as I realized it was Urokodaki-Sensei placing his hand on my shoulder. I moved my eyes down to my hilt, how did he remove the sword without me even noticing? I know that he was a Hashira once but still.

"I can somewhat figure out what you are thinking" He began, tightening his grip on my shoulder "But, it isn't a good idea to rush the final selections. You have the highest potential I have seen till now, and I do not want you to waste it"

"I understand," I said, moving my shoulder so as to remove Urokodaki-Sensei's hand "But, I need to, I can't waste more time. I wish I could explain my circumstances to you, but I can't, at least not right now"

Urokodaki-Sensei looked at me contemplating my words. I don't mind telling people about my ability to travel worlds, but I can't do it at least until I am powerful enough to be one of the strongest in the world or be acquainted with one of the strongest. The Hashira are not the strongest in this world, only the upper moons and Muzan are. So, until I am powerful enough to defeat the demon king, this secret will stay shut.

Urokodaki-Sensei suddenly vanished from in front of me in a burst of speed, somehow not making any noise. A moment later he reappeared, holding an old worn-out map in his hand. He opened the map, shaking off the dust from it.

"This" Urokodaki-Sensei began "Was something I once devised as a training plan, but none of the disciples I've had met the qualifications to use this. Most people take an entire year or two to absorb just half of my teachings, but you have managed to do so completely in just three months."

He presented the map in front of me, revealing it to be a detailed map of a nearby mountain. I blinked, looking at the map in front of me. For this era, this map was one of the most well-detailed maps I have ever seen. Considering this world doesn't have something like Google Maps, does that mean…

"Did you make this map Sensei?" I asked, seeing not only various important spots, but at least a dozen routes, both hidden and in the open leading to it. "It's extremely detailed, this must have taken months to make"

"Years" Urokodaki-Sensei grunted. "A mountain far away from here, I asked the Slayer Corps to help me in making an easier version of the final selections. It's surrounded by Wisteria and has a very low amount of demons in it with some safe points on the way, unlike the real final selections where the only safety present is the sun."

"Originally, I intended to make this a form of test before taking the real final selection, but the disciples I've had took multiple years to master my teachings. The rare ones talented enough to learn Total Concentration in a short amount of time were powerful enough to pass the final selections on their own."

Urokodaki-Sensei slightly gripped the map "but I miscalculated. They failed the exam and died, and only one passed. I often wonder if I should have let them take this course before sending them off to their deaths"

Urokodaki-Sensei handed me the map "No one has been here for the years. The demons inside are either dead or extremely weak from starvation. It's perfect for someone like you. Again, I'm asking you, if you're truly sure you want to do this and not train for another year?"

I took the map from Urokodaki-Sensei's hands. This map had real demons. If I made even a slight mistake, I would be killed and eaten. The risk was immense, but if I passed this, I could become stronger much faster.

"I'll do it Sensei," I said rolling up the map. "And I promise, I'll forever end the era of Muzan Kibutsuji."

"Then off you go," Urokodaki-Sensei said turning around "Once you've passed, come back and meet your junior as well. It's not polite to run off without meeting your junior once, but you lack time, every second counts"

I nodded, as I rolled up the scroll. Bowing to Urokodaki-Sensei, I turned around and sprinted out of Mt. Sagiri. What usually would have taken me hours to traverse this mountain, only took me minutes as I sprinted out with inhumane speed.

Unrolling the scroll, I studied the route to get to the mountain. It would take a normal person an entire month to reach this mountain, but it'll only take me half a week to reach it. I pocketed the map, only to find my hand brushing against an unfamiliar sword.

I looked down, only to see that in my empty hilt resided a Katana. I took it out, feeling it's weight and deducing it to be slightly heavier than the normal steel Katanas. I looked at it's design, finding it to be half blue and half black. The sword gave off a sort of warmth, like the sun as I held it in my hands.

This was a Nichrin Katana, or to be more precise, Urokodaki-Sensei's Nichrin Katana. He probably switched it out just like he switched out my normal Katana. I sheathed the Katana back, hiding it under my Haori.

Now then, it's time to start an intense 2-month training arc.

—---------

*BANG*

A huge sound echoed as if the wind itself was screaming in pain. I appeared as the force from me suddenly stopping produced a huge gust of wind. Silently wincing at the huge amount of sound produced which could alert demons, I turn towards the mountain bathed in moonlight.

To the untrained eye, it would look like a normal mountain, but I could clearly see slight traces of pink hidden behind the normal green color of the trees. It looks like the Wisteria trees were hidden beneath the normal trees to hide them from demons or civilians.

Clutching my Nichrin, I silently tread toward the mountain. The map showed me a safe house in the middle of this mountain surrounded by Wisteria trees. For now, let's just find that while being wary of demon attacks.

Pocketing the map, I silently sprinted towards the mountain.

As soon as I went past the wisteria trees, the atmosphere around me completely changed. There was no sound barring my footsteps. Usually, you would hear some insects like grasshoppers, the chirping of birds, and maybe even a wild animal.

But this area was completely silent. It looks like the demons here ate up everything on this mountain. This means that even if the demons here are weak, their quantity must be humongous.

I unsheate my Katana. I couldn't waste time unsheathing my Katana if I was ambushed by a demon. Keeping my ears and eyes on full alert I ventured deeper into the mountain.

—-----------

"Foo, found it"

Sheathing my Katana I looked at the worn-down shack in front of me. Around me were heaps of Wisteria trees. Plucking out one of its leaves, I look at it turning it around on my hand. Maybe it glows because it absorbs the sun's rays better than other plants? I'll bother about it later

Still, it's strange that I didn't encounter a single demon on my way here. Maybe there weren't any demons left? Or could they be so weak that they got scared of a slayer? No, they might be planning something instead, like an ambush.

Normally one would have to manage their resources and somehow obtain food sparingly, but I could simply go back to the MHA world, eat some exquisite food, and come back. While this isn't recommended, I have no other choice.

I did not encounter a single living being on my way here, not even mosquitoes or flies. This was a total wasteland.

Now then, I've stayed in this world for around three months and I have the final selections in just a month. While traveling here I realized that there was no possible way for me to hone my basics enough to be able to survive the final selections.

Which is why, I will be going back to get something that can help me.

Closing my eyes, I call out to the void. Opening my eyes, I find myself before the familiar view of the purple nebula-like Kaleidoscopic void. I turn around, willing the fragments to appear back on my hands. Sorting out the fragments I pick out the MHA fragment.

The environment around me changes instantly. No fancy portal, now whirlpool, no elongation, no nothing. Just pure simple teleportation. I quickly take out my phone looking at the time and date.

I was in the Demon Slayer world for three months, but only three days passed here. Looks like there's some form of time dilation between these worlds.

(A/N- Don't try to calculate these time dilations, they're just a plot point for me to place the MC in any arc I want to)

Wait, three days? What about my classes?

…

"FUCKING SHIT, I COMPLETELY FORGOT I'M STILL IN SCHOOL"

I quickly ran to my cupboard, scrambling around my clothes as I put on the UA uniform. With no time to eat or check my timetable, I shove all the books in my bag. Quickly grabbing my lock I run out of my apartment towards the nearest subway station.

—---------------

I sigh as I turn my phone off. It's been three days, and yet I did not get a single notification from anyone, they were still in the hospital being cared for. What a great way to ruin my mood.

I sigh and sink back into my seat on the subway. After staying in a technologically primitive world for three months, everyday common items like the subway suddenly felt so advanced. I missed this feeling of lazing around while on my phone.

Nevertheless, on my phone are multiple prototypes I've been developing to help me master my breathing technique and kill demons. I discreetly take out of the Wisteria petal kept in my pocket that I'm going to use to develop a form of toxic gas bomb for demons.

I flip over the tabs on my phone each displaying multiple prototypes. Apparently, the breathing techniques I've been using not only enhances my physical abilities but speeds up my internal capabilities as well, pumping blood faster, slightly faster regeneration, enhanced thinking capacity, and comprehension.

In a matter of minutes, I've already developed three prototypes.

The first is a gas mask. The mask was inspired by Jojo's Bizzare Adventure part 2 where Lisa Lisa gave Joseph a special mask that only allowed him to breathe in a specific pattern to constantly generate Hamon. The principle for this device is the same but with breathing techniques.

The second is a UV bomb. Just like a normal flashbang, it lets out a large flash of light. However, instead of normal light, it releases a huge burst of UV rays that should, theoretically, reduce demons to ash in a minute.

The third was a UV lamp. This was basically a lava lamp but it radiated UV rays instead of normal light. I could just modify a normal lava lamp, and possibly extend the Lava lamp's range. I'd need to make it solar-powered too, there were no batteries or electrical outlets in the Taisho era after all.

A sudden jolt woke me out of my mental monologue. I look up, seeing that the subway has stopped at my station. Quickly pocketing my phone, I step out of the subway before the doors close on me. Walking out of the subway, I order a taxi to get to UA.

While I could travel to UA by foot with my breathing technique, I would be quickly caught by the police for using my Quirk. While that isn't that big of a problem, the real problem is that I don't have a Quirk. It would be difficult to explain to the teachers about my suddenly possessing a Quirk.

I will have to tell them one day, but that isn't today.

—----------------

*Boom*

"MEI HOW MANY TIMES HAVE I TOLD YOU TO STOP EXPLODING THE WORKSHOP?"

"I'M NOT EVEN MAKING ANYTHING RIGHT NOW"

"THEN WHO THE HELL WAS THAT?"

"It was me"

Power Loader, the teacher of the support course quickly turned around, jumping back as he immediately settled in a combat position. When he saw it was just me, a student wearing the UA uniform he let his guard down.

"Oh, it's you, Mei's friend" Mei's friend? Did he not even know my name?

"Um, sorry Sensei for not attending classes for the last 3 days. It's just that I was sad and disoriented after hearing what happened in the USJ. I had some friends in there and I've just been worrying about the-"

"Calm down, there were no classes the last three days"

"Huh?"

"UA declared a week-long holiday you didn't miss any classes, um, student."

That…that makes a lot of sense. It wasn't just the students that were affected, but the teachers too. There was most probably a lack of teaching staff for the classes, so they didn't have any choice but to declare a holiday.

"Still, it is really admirable how much you care about your friends, that's a very admirable quality you have that I have, unfortunately, seen a lack of in this generation. Also, don't worry your friends are being tended to by the best doctors in the country. Say, what is you-"

"MUMBLE MAN"

A huge shadow loomed over me, before crashing into me. I sensed the presence long ago, but didn't bother dodging it. Little did I know that instead of coming up to me and giving a pat or maybe a fairly strong smack on the back, Mei Hatsume would fucking jump with her entire body weight on my back.

I immediately balance myself from the unexpected tackle. If it was the previous untrained me I would have fallen over and be in the same hospital as 1A.

"Brrruuzzzaaaa! You have nooo idea how slow it has been making babies without you." Without context, that would sound wild. It still does with the context though.

"Oooh what's this" Mei said moving her hands around my shirt "I mistook these for boobs but they are some seriously large pecs and- ooh are these abs? When did you get so ripp-"

I tuned out what she was saying, as I felt her soft hands scavenging my body. All the way from my abdomen to my chest and to my arms. The sense of softness on my back didn't help either. I couldn't just turn around, grab her chest and remove her from me could I now?

Actually, that might-

"Mei, stop harrasing him"

"Eh? Don't worry, I'm sure he doesn't mind, besides, I'm sure he's been-"

Before Mei could finish her sentence, Power Loader tore her off my back throwing her away into a pile of unfinished support items. Mei immediately got back up with a smile, as if the throw didn't bother her at all. I took a deep breath to calm my nerves after this entire ordeal.

"Sorry Mei-chan, but I'm here to make some support items on my own, I promise I'll help you later"

"WHA? No way, just look at my babies. This is a special Jet pack I made that has enough power to send you above the atmosphere, or this tactical capture net that also discharges 10,000 Volts of electricity or-"

"That's enough Mei" Power loader cut in, swinging his arm "He clearly has something to do, just leave him alone for now. He said he'll help you later right? Besides, it's about time you go home"

"Nuh-uh" Mei replied shaking her head "I'll make WHATEVER I want WHENEVR I want, innovation has no time limit, besides, you never know if the next thing I make will end up as a cornerstone in history. I might be the head of the UA Support course when I grow up for all it matters"

"I just hope it's a good cornerstone you make"

I shake my head in exasperation as I tune them out. I head into the support workshop with my prototypes to get to crafting.

Heh, Minecraft

—--------

*That really loud flashbang sound effect from "Think Fast Chucklenuts"*

"FU-MEI WHAT DID I TELL YOU ABOUT RELEASING THE FLASHBANG NEAR ME?"

I cover my eyes, still seeing patches of white even in the pitch black of my eyelids. I was working on the gas mask and figured I'd ask Mei to help me make the UV flashbang and the UV lamps.

Unfortunately, she doesn't know the first thing about listening to instructions or warning others.

"Get over it" Mei waved over dismissively "Besides, aren't flashbangs that use UV rays too boring? Why don't we add something like uh, OOH, how about making it spew out flames too, OR OR, how about it releases a really really loud and piercing sound?"

"Mei, I'm going to be affected by the sound and the flame too," I said, finally opening my watery eyes and getting used to normal light. "If you want to help, make its range bigger or make it release more UV rays, not turning it into a fucking bomb"

"Mouu" she pouted "You're no fun AYD-chan"

She said nothing as she went back to making more flashbangs. Surprisingly, there weren't any explosions whatsoever. When I looked over, I saw a completely focused expression completely different from her normal face or jovial mood.

"You can look like a decent support item maker huh?"

"The hell is that supposed to mean?"

I didn't say anything as I put on the mask. The mask had special pathways that lead to pores on the surface which were used to suck in air. If I breathed in normally, the air would just dissipate back into the atmosphere. Only if I use water breathing, will the air travel through the special pathways and come to my nose.

I try to breathe in normally, as no air reached my nose. I then used water breathing, finally receiving an influx of air. If I put this on at all times, I'll master Total Concentration: Constant in no time.

"I don't get why you're making this stuff," Mei said placing another flashbang next to a pile of them. "Babies are supposed to be wild and exciting, something COMPLETELY out of this world, not so plain. Besides, why did you even make that mask? Doesn't it just make it more difficult for you to breathe?"

That's what the point of the mask is.

"Just some props"

"Mmm, you have that look on your face"

"What look?"

"It's the same one you used to have when we were younger. Whenever you're hesitant about something you furrow only one of your eyebrows"

My eyes rise to my eyebrows, only to find them perfectly straight.

"So you are hiding something huh?"

I waited for her to say something, but she just kept quiet making more flashbangs.

"Aren't you going to ask?"

"Nahh, not my style. I'm not interested in dark depressing stuff, or some type of heroic speech, or just…backstories in general. The only thing I really care about is making more babies. Besides, we promised each other not to pry into each other's secrets didn't we?"

"Though I do admit" Mei started "it does pain me a little that you feel like you have something you can't trust me with, but I trust you enough to not bother you about it. So, when you feel comfortable enough, I'm all ears"

That was...surprisingly sensible. I didn't expect something like that from her based on her personality from the manga. Then again, her screen time was just barely above Tenten's so there wasn't a lot to show in that time.

And that manner of speaking, were we friends when we were children? Is this the cliche childhood friend trope? I got run over by a truck so I can't completely rule it out. Besides, doesn't the childhood friend never win in the end?

That aside, I should complete my inventions for now.