Reborn in Naruto world with demon slayer powers

Morning 5 AM Private Training ground:-

Arriving at the exact time I saw everyone present including Guy, Neji said "You are late!" I replied " If you are 3 Minutes early, it doesn't mean I am late, I know the time" Neji was always irritated because my fighting style had changed his and he started using all types of dangerous moves which were not to be used by an 'honourable noble person' not that Yoriichi cared, in a fight its either 'I kill you or you kill me', it was learned by reading about his clan's history about demon slayers, it was about either they die or the Demons die, it was a battle of rage, vengeance, Hatred and it was going on for around a thousand years.

( The same as the original Demon Slayer)

When Yoriichi Read that, He understood that things are different here and His powers are still needed in the future. It had been 50 years since the end of the last Human-Demon war and since then no one has become Hashira as Most of them travelled here to protect the bloodline from extinction.

Guy sensei asked us about our basics and about the Kekkei Genkai, Neji explained his positive points about his Kekkei Genkai and when it was my turn I just unsheathed my blade and showed the flames and said about how my cuts with the fire hurt a lot and it does not heal and leaves trauma.

(same as Demon Slayer)

He asked about the Mark on my head and I asked him about the 8 inner gates, and he understood that it's a forbidden secret technique, which it actually is at some point, not that I am going to explain it but he still asked me if there is anything very dangerous about this technique and he was even willing to tell the secret about the gate of Death, I understood he was genuinely concerned so I explained about how it is not a dangerous Technique but it reduces the life expectancy to 25 years. Guy was a little shocked as reduced lifespan was a dangerous thing but Yoriichi explained how it does not reduce lifespan to 25 years if I have chakra control, not that I am going to explain that nature energy is solving that problem for me and as long as I have chakra my lifespan will not reduce. (The protagonist has to keep some secrets.)

I knew that using nature's energy and making my body strong would not reduce my lifespan and force my life force to become stronger instead, not that it mattered more, Life and Death are not something I can decide when I am weak, if I am dead then life force doesn't matter. If I am alive then I can get a thousand years. Living is not easy and that was something I understood when I saw Naruto, I could have helped him but it is not my time to interfere and to survive I have to become stronger not for Naruto but for me as I know things won't go as planned. He is the safest person in this village and he has to be protected but no one would care if I die tomorrow, maybe parents would burn half the village and the old fox but that is all.

Getting the training started, we did a thousand pushups, sit-ups and frog jumps. I asked, "What is the point of walking on hands around the village?" Neji also supported my question while Lee was just jumping to get started, I do not understand where his energy comes from. Guy didn't explain and said something about youth, and started walking or not walking, I don't understand what to call this process of walking on hands.

Neji and I did not join them, but we waited for them to come back, We had a spar in taijutsu, Neji did not like me every time I tried kicking his balls so, he became an expert in blocking kick to balls. He would just kick me on the foot when I tried to hit at the balls, and that block was not good for me, every time he blocked, my legs would hurt badly and to block the kick like that. one should be fast enough to quickly block the kick with the foot, which he developed like instincts. If it was someone else his leg would have been broken, he had made his reflexes adapt to my style because I learned by fighting him every time and changed my style in a way that would be unpredictable and lethal.

Trying to make my own martial arts, combining extracting and re-building again and again. Because of the demon mark, I have opened up to all the potential and talent. I can use the body to like the 8 gates, but even higher burning the spiritual energy. Demon mark allows one to use his body's full potential, awakened when a person is ready to sacrifice himself for the awakening of his potential, on the condition that the person has not lost hope in a life and death situation, where he knows his certainty of death. Yoriichi's situation was different as he was already ready to use and capable of handling its curse, the difference between the awakening of the demon mark and sharingan is very different, for one it's a curse of blindness while for others it's a confirmed early death. One has to lose someone important while the other has to accept his death for a power which is a curse.

It is also possible (in theory) that the demon mark manifestation for the Uchiha is the sharingan with a less cruel end, and the theory of early death because of the demon mark is the exhaustion of physical energy (life force) which also happens in uchiha, Who bleed on eyes because of weak physical energy, unable to recover the energy leads to death of cells and causes permanent blindness, when using transplanted eyes which does not belong to the user, the user is not able to master its powers and it just becomes a tool with power and can be used repeatedly (I am not explaining other variables, deal with it yourself)

The strength of chakra is the understanding of its use, It's like how a kid does not know anything but as its understanding increases, its growth increases. If you know about chakra control, manipulation and techniques your growth in chakra strength increases, it also requires instincts for some things. There are 12 basic hand signs and it is publically known as they correspond to the 5 elements, yin and yang. 5 elements include all the 5 fingers and yin and yang for each hand. Different signs react to different elements. Joining both hands together makes the connection of all elements and union attracting natural energy from nature to oneself.

I saw Sensei and Lee coming, our training continued and we learned new taijutsu skills. From watching Bleach I understood that in swordsmanship speed and stamina are everything so I need huge reserves of chakra and extreme speed, to defeat others before they can even see me or start moving or doing hand signs. For one I knew, shun-shun was not going to work. I'm not Shisui so I have to make my own technique.

So I'm going to create a similar technique. To others, it would look like I just teleported but in reality, it would be different! I can use thunder breathing but it would be too loud and energy consuming.

I need 'transparent world' to do it. And for it, I have to wait for my eyes to be strong and get a hint of sword energy. Anyone can get a transparent world as long as their eyes get a hint of sword energy and they are capable of cutting anything. The eyes won't be able to see past anything it is not capable of cutting.

Next Chapter:- Creating a movement/footwork technique.