Slayers and Heroes (BNHA x Demon Slayer Crossover)

4: Explanation

(Yo! By the way, Muichiro isn't actually a girl, it's only written that he's a girl because of Deku's POV. I'm sure I'm not the only one who saw the anime and thought he was a girl. Feel free to skip parts of this chapter if you already know the background. Tanjiro POV will be coming soon in this chapter, but for now...)

3rd Person POV

"T-Taisho Era!?" All the young heroes in training thought. Even the pro heroes didn't have much to say.

"Do... you think you could tell us more about your.... time period? In exchange we will give you information of ours" Cementoss reasoned.

"That sounds like a wonderful idea" Ubuyashiki accepted the request.

"In our time, man-eating demons have been preying on humans for hundreds, if not thousands of years. So an organization founded by my family called 'The Demon Slayer Corps' was created to eradicate the demons. Demon Hunters such as my children have been protecting the humans since then. However our organization has not been officially recognized by the government.

These demons have enhanced strength and speed incomparable to humans. However, the Demon Hunters have found a way to defeat a demon by using Breathing Techniques that allow a human's speed and strength to match that of a demon.

The only way to kill a demon is the sun and decapitation of a Nichirin blade, an ore bathed in the sun all day long. The Nichirin blade is also known as 'the colour changing sword' as it changes colour to match its owner." He finished.

Breathing Techniques? Everyone questioned internally. How does breathing air enhance a persons abilities?

"Pardon, but could you explain to us these... Breathing Techniques?" Aizawa-sensei's tone was skeptical. His face covered in bandages.

"Ah yes. I may be the Master, but I do not know anything about how breaths themselves work. Giyuu-san, would you like to explain?" He asked.

"Oh, Yes master." Hesitant at first, but it was a request from the master, in which Tomioka accepted. He was never the best at socializing, or good with words. So he tried to remember the way Urokudaki-san had explained to him.

"Breathing Techniques. Allowing great amount of oxygen into ones bloodstream and have it flow throughout your entire body. It allows increase in stamina, strength and speed by excelerating your heart rate and increasing your blood pressure.

The first breath ever created was Breath of Sun. Other core breaths such as Water, Wind, Flame, Thunder, and Stone are branched out from Breath of Sun. Other breaths are branched out from those five. Each breath has a unique breathing style and form.

Even focusing on breathing can clot deep wounds and prevent any further bleeding. Another breathing technique is Total Concentration: Constant where one inhales a maximum amount of oxygen in a specific pattern every second of the day. Even while sleeping." Tomioka finished.

Tanjiro remembered his training in the Butterfly Estate. Mastering the Total Concentration: Constant sure was tricky. He cringed at the memory of when he failed to keep up the breathing while sleeping and he was pounded by Naho, Kiyo, and Sumi. He looked to his left to see the three girls waving at him. This brought a smile to his face.

For the entire of class 1-A, it was a lot of information to take in. Even for the pro heroes. Of course, no normal human would think that breathing air could be so powerful. Then again, their world isn't exactly the definition of 'normal'.

'Breathing Techniques. Man-eating demons. Demon Hunters that kill demons and protect humans, much like how heroes protect civilians from villains.' Midorya thought. If he had his notebook he would've written everything down. That's when he remembered something previously mentioned.