Mystic Demon Slayer

{One-day latter}

Zenitsu can be seen doing various exercises every one of them with the objective of improving one or multiple aspects of his body, they were specially designed by his master

At the start of the training it was a bit easy but Jigoro was quick to notice this, so he tested him a bit and the look on his face was quite the sight to behold as he discovered the huge Increase in physical power from what he knew before but he attributed it to the lightning bolt as it had changed some of zenitsu's looks and personality so maybe it also changed his body

And so he kept on increasing the level of difficulty bit by bit till he felt it was enough and so he just sat there and watched Zenitsu get tortu… trained

'That old man sure is ruthless, It feels like leg day allover again… hmm, but what's even leg day I don't remember… anyways as much as I hate this I have to train and get stronger I don't feel secure living in a world where some random demon can kill me'

And equipped with resolve Zenitsu long and painful training journey began

* * *

{2 Years Latter}

Hufff….Huffff...Hufff

'That was tiring today master made it even harder, every time I get used to the training it gets harder sigh… but I got waaay stronger than I was 2years ago and my rate of improvement doesn't seem to be affected as I got stronger'

'Gramps said that he had never seen anything like this and he probably linked it the lightning strike changing me, not that he is wrong as it removed some kind of limiter In my body'

'Thinking about it I am almost done with my own breathing technique maybe in a couple of days just in time for what gramps called "Going out to get experience" he said he will take me to see some demons and the reason why we kill them, I'll just take a rest before I make some final touches to the breathing technique'

* * *

A couple of days later a 13 years old kid can be seen sitting cross-legged breathing in some sort of mysterious pattern as golden thunder flashed around him from time to type, but suddenly he stopped as he gasped for breath huffing with sweat dripping down his forehead

'That was dangerous… I finally finished it, it is way stronger than the Thunder breathing technique but it also puts a lot of load on the body and lungs while the Lightning concept keeps 'hammering' the body to make it faster and stronger, all I need to do now id just make the sword moves to accompany it and maybe somebody techniques… sigh probably a year or two of intense training'

'but on the happy side of things if I am able to use it 24/7 my body will keep getting stronger without me doing anything but I need to get my lungs way stronger than it is now as it is too frail I need to think of a way to strengthen them, ill ask gramps latter he may know of a way to do so, as for my body It is simpler all I need to do is train… too much stuff to do its soo tiring… but it'll be worth it in the end… I think'

'But what should I name the technique I mean It is different from what it used to be, Thunder is just the sound that accompanies lightning they cant be compared and the technique is full of lightning concept… whatever I was able to comprehend without this body exploding at least…i'll think about it later I have to rest a bit before going with gramps latter...'

(A/N: Give me some name suggestions...)

And with him Finishing this train of thought he just collapsed back into the bed as he fell asleep almost instantly

* * *

The following morning Zenitsu can be seen standing in from of Jigoro as the latter started talking slowly but seriously

"Today we'll search for some demons to hunt… I want you to see what you will be up against"

"Okay gramps"

At this point of time, Jigoro had already given up making him call him master so he didn't care anymore, so he just nodded and started running with Zenitsu following him closely

'shit, this old man may be old but he is still strong…'

'talking about strength I wonder how strong I am compared to the demons and demon hunters out there… It doesn't matter much tho as in the next couple of years ill enter a fast growth period… I'm looking forward to what this world has to offer...'

* * *

{A couple of days later}

Zenitsu and Jigoro could be seen walking towards a small house which for some reason seemed gloomy and giving off some weird vibes

"Gramps, this place is weird..."

"No, we are in the right place I can sense a demon follow me.."

And without further talk he ran towards the house with Zenitsu sticking close to him noticing this Jigoro smiled happily 'This kid.. he's getting stronger, after we go back ill train him harder, if he keeps at this rate he'll become a pillar in around 3years… but the breathing technique he is using… it is not the thunder breathing technique… similar but not the same, ill ask him about it when we go back, right now we have to be fast we may find some humans still alive if we are lucky'

And in a matter of seconds, Jigoro and Zenitsu stood at the door of the small house each with a different expression Jigoro just looked calm but one can see the anger in his eyes but Zenitsu looked visibly mad and disgusted as his body started flashing with golden lightning...

'So this is what Gramps wanted me to see… so this is what demons do… kill humans… feed on humans… so they just see us as food' closing his eyes slowly before opening them up with newfound resolve 'SO ILL JUST KILL THEM!'

Inside the house 3 kids, no what is left of the 3 kids were thrown all over the place as a demon stood in the middle eating slowly as if enjoying a gourmet meal, but noticing the uninvited guests to the dinner it got mad as it turned slowly before jumping towards them

Just as Jugoro was about to move Zenitsu raised his hand to stop him as he flashed and appeared behind the demon in a burst of lightning, turning his head Zenitsu just looked slowly at the demon disappearing as it died slowly with no remorse in his eyes

But Zenitsu wasn't focusing on this scene, as he looked at a completely different world, as the moment he saw the kids dead and killing the demon himself something broke inside of him… A Seal of sort broke opening a new world to him

**** Author ****

Help me with names for the techniques and moves, thanks :D