Hidden away in the mountain cabin, Kanae Kocho began her lessons, teaching Tetsuya Kamihara the fundamentals of Breathing Styles.
Breathing Styles were specialized breathing techniques utilized by the Demon Slayer Corps. By inhaling massive amounts of oxygen, a swordsman could drastically enhance their physical capabilities, granting them the superhuman strength necessary to stand toe-to-toe with demons.
Passed down for centuries, there were five foundational schools: Water, Thunder, Flame, Stone, and Wind. Particularly powerful swordsmen could use these five primary forms as a base to develop their own unique derivative Breathing Styles that better suited their individual physical traits.
Kanae's Flower Breathing was a direct offshoot of Water Breathing. Because of this, aside from her signature Flower Breathing, she also possessed a deep understanding of Water Breathing.
Since Tetsuya's baseline demonic physique already far surpassed the vast majority of Demon Slayer swordsmen, he didn't need to undergo any brutal physical conditioning. He skipped straight to the actual breathing exercises.
"Haa... Haa..."
Under Kanae's meticulous guidance, Tetsuya carefully controlled every wisp of air he drew into his lungs, vividly feeling the oxygen circulate through his system.
Flooded with massive amounts of oxygen, his cells responded by feeding a surge of raw power back into his body. It started small, but the accumulating strength was impossible to ignore.
'So this is a Breathing Style?' Tetsuya thought, completely dropping any lingering underestimation he had harbored. Demons possessed immortal bodies at night and magical, overwhelmingly powerful Blood Demon Arts. For the Demon Slayer Corps to wage war against them for a millennium, these Breathing Styles definitely had their own incredible merits.
"That's amazing! You're picking this up way faster than I did when I first started learning," Kanae praised, clapping her hands with a bright smile.
"It's all thanks to my great teacher," Tetsuya replied, engaging in a bit of polite mutual flattery.
Honestly, it wasn't something to brag about. Between his overpowered demonic constitution and having a patient, beautiful former Hashira tirelessly guiding his every breath, even a pig could probably learn how to fly under these conditions.
"However..." Kanae's delicate brows furrowed. Just as she had suspected, neither Flower Breathing nor Water Breathing was a good fit for Tetsuya.
Water Breathing required a calm, steady mind completely free of distractions—a heart as tranquil as still water. Compared to the other styles, Water Breathing was the most fluid and the easiest to learn. A skilled user could unleash agile, flowing strikes accompanied by torrents of water-like sword aura.
Flower Breathing shared very similar characteristics.
Kanae could sense that Tetsuya’s inner nature was a bit too turbulent and aggressive for such fluid styles. He was likely much better suited for the overbearing, fiercely offensive forms like Thunder Breathing or Flame Breathing.
Because of this mismatch, she could only teach him the fundamental mechanics of Breathing Styles in general. However, Tetsuya's comprehension speed was staggering; in just a few short days, he had completely mastered the basics.
"Well, I guess I don't have anything else to teach you," Kanae chuckled wryly. She had been so excited to pass on all her skills to him, too.
"This is more than enough," Tetsuya assured her. Clenching his fists, he reveled in the newly enhanced power surging through him. Even though he had merely scratched the surface by learning the absolute basics, he could clearly feel a significant boost in his overall combat strength.
"The next issue is figuring out how to actually get you into the Demon Slayer Corps," Kanae mused aloud. If Tetsuya wanted to learn the other Breathing Styles, officially joining the Corps was his only option.
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But the Demon Slayer Corps would never knowingly accept a demon into their ranks. Furthermore, since demons couldn't touch sunlight, Tetsuya would be strictly restricted to moving at night—a massive red flag that would instantly arouse suspicion.
Seeing Kanae's troubled expression, Tetsuya waved it off. "As long as I can officially get my foot in the door, it's fine. I'll take care of the sunlight problem myself."
Kanae blinked in surprise. The longer she stayed with Tetsuya, the more he astonished her. Judging by his confident tone, he actually possessed a surefire way to overcome a demon's ultimate natural enemy.
She didn't press him for details. When Tetsuya felt the time was right to share his secret, he would tell her.
If getting him past the front door was the only immediate hurdle, that wasn't actually too difficult. "How about joining as a logistics or support member?" Kanae suggested.
"A support member?" Tetsuya's eyes lit up.
He had almost forgotten about that. The Demon Slayer Corps wasn't entirely made up of frontline swordsmen; they relied on a massive network of support personnel to function. There were the Kakushi who handled the aftermath of battles and corpse retrieval, the Cultivators who trained new recruits, the medical staff at the Butterfly Mansion, and the various attendants maintaining the Hashira dojos.
The damned system's exact requirement was simply to receive "official recognition from the Corps," not explicitly to become a combat-active Demon Slayer.
He could easily infiltrate the support division first, secure the Immunity Physique reward, and then look for opportunities to learn a Breathing Style. Taking that route would dramatically lower the difficulty of his mission!
"I'll write you a letter of recommendation. When the time comes, just say I wrote it before I died. With your incredible medical skills, getting accepted into the Butterfly Mansion shouldn't be a problem at all," Kanae smiled brightly. It was the perfect solution—she could even have Tetsuya keep an eye on her younger sister, Shinobu, while he was there. Killing two birds with one stone!
Tetsuya offered a meaningful, wicked smirk. As the old saying goes, it's easy to guard against a thief outside, but impossible to stop one inside the house. With a former Hashira personally paving the way for his infiltration, even the most impenetrable fortress of the Demon Slayer Corps was bound to have a gaping hole dug right through its walls!
The two spent the next while hammering out the finer details. Kanae briefed him on the standard operating procedures of the Demon Slayer Corps, ensuring that when Tetsuya finally walked through those doors, he would look like he entirely belonged there.
Naturally, Kanae held back any highly classified, sensitive intelligence. She didn't breathe a word about the exact location of the Corps' Headquarters or the identity of their core leader, Kagaya Ubuyashiki.
A short while later, a heavy wave of drowsiness washed over Kanae. Her small face grew slack as sleep threatened to claim her once more.
Tetsuya secretly shook his head. The windows of time Kanae could stay awake were shrinking by the day. Was her body reacting just like Nezuko Kamado's? Because the extreme physical toll of demonification was so massive, she might need to sleep for years just to fully recover her energy.
With him preparing to join the Demon Slayer Corps, he couldn't exactly just abandon the sleeping Kanae in the middle of a barren wilderness.
Brilliant as she was, Kanae had obviously realized this dilemma as well, but she didn't have a solution. Every single person she knew and trusted had been deeply scarred by demons. None of them would ever believe a word a demon said.
She and Tetsuya were anomalies—outcasts rejected by demonkind and fiercely hated by humanity.
"I know the perfect place for you," Tetsuya said, a sudden flash of inspiration hitting him. There was only one person in the entire world who could truly understand their bizarre predicament.
Kanae blinked curiously. "Who?"
"The great fugitive among demons!" Tetsuya chuckled. It was high time he made contact with the ultimate support character of this universe.
...
When the two finally stepped out of the cabin, they were immediately awestruck by the sheer beauty of the deep mountain night sky.
The night was pitch-black, but a crisp, cool wind swept through the forest, rustling the branches in a soothing, rhythmic whisper. A pristine, bright moon hung high above, flanked by a sea of dazzling stars that bathed the earth in a brilliant silver glow.
The breathtaking, picturesque scenery was enough to make a fresh swell of hope bloom in their hearts.
"Tetsuya! Big Sister Kanae!"
Rinka Akiyama's petite, delicate figure suddenly darted out from the nearby woods, shouting their names with infectious excitement.
Watching the cheerful, overly energetic girl bound toward them, Tetsuya and Kanae exchanged a knowing, warm smile.
Demons didn't actually need to consume normal human food, but deeply ingrained human habits were hard to break in such a short amount of time.
For the seven or eight days they had been hiding out in this remote mountain, Rinka was the one secretly hiking up to deliver their meals.
The food didn't provide Kanae any actual nutritional value. At best, it let her taste the flavors and offered a phantom sense of fullness—but more importantly, it brought her a deep sense of psychological satisfaction and comfort.
The three of them finally left the deep mountains behind, setting off toward their new destination.
Asakusa, Tokyo Prefecture.