Tanjiro's father had always been frail and sickly. It was unclear whether this was a congenital condition or a result of practicing the Sun Breathing technique for too many years.
However, he possessed something others did not: the Transparent World. When faced with a giant bear several meters tall, his breathing remained perfectly calm, and he could slay it with his eyes closed.
Tanjiro's father usually spent his days at home recuperating, almost like a plant. Only during the winter, each year, would he light a bonfire and perform the Hinokami Kagura dance all night long.
When Tanjiro was young, he asked his father why, despite his frail body, he could dance through a cold winter night without issue. Tanjiro's father told him that this Kagura dance was inherited from his own grandfather. When his father was younger and in better health than he was then, he would still be out of breath after dancing.
Later, he came to understand that the key lay in the breathing method and the precision of the movements. Realizing this, he strove to correct both his movements and his breathing. Then, one day, some years later, a transparent world suddenly appeared in his mind.
And this was the [Domain] that only the strong, those who had exhausted every last ounce of their strength in a painful struggle, could comprehend.
"It was only much later," Tanjiro finished, sighing, "that I understood. When Father took me with him that night he killed the bear, he intended to teach me the secret to that [Transparent World] he saw..."
"Unfortunately, my father passed away less than ten days after that night. My aptitude is too poor; I couldn't comprehend that [Transparent World]."
Uchiha Nagi and the Flame Hashira listened quietly as Tanjiro recounted his family history. Nagi, however, had a sneaking suspicion that Tanjiro's father didn't die from exhausting his potential killing the bear, but rather because Tanjiro's mother was too beautiful.
One look at Tanjiro and his sister's features was enough to tell. Marrying a beautiful wife, then toiling in the fields day after day, and having a large brood of children… for a man already frail, working himself to the bone like that, it would be a miracle if he didn't die young…
Oh, right. They lived on a mountain, weren't landowners, and the entire family's sustenance depended on a sickly patriarch. Farming and chopping firewood by day, then 'plowing the fields' and making babies by night—an early death wasn't surprising at all…
Rengoku Kyojuro, hearing Tanjiro speak of this "transparent world," realized it was very likely the Transparent World he knew of. The Flame Hashira was ecstatic.
True to his straightforward and cheerful nature, Rengoku Kyojuro, the big brother Flame Hashira, never beat around the bush. His large eyes wide with excitement, he said to Tanjiro, "Well then, young man! Would you be willing to show us your family's Kagura dance sometime?"
Tanjiro scratched his head, smiling sheepishly. "Of course, I can. Whether it's Rengoku-san, Nagi-niisan, or Inosuke, I don't mind teaching the Kagura dance to everyone. I'm just not sure if the Kagura dance is related to the Transparent World Nagi-niisan mentioned."
Uchiha Nagi looked at Tanjiro seriously. "Thank you, Tanjiro. I would very much like to learn your family's Kagura dance."
Lying to Tanjiro was impossible; it was better to be honest. He possessed a divine sense of smell, capable of detecting the seven human emotions and six desires. He could sniff out lies and truths alike—a truly unscientific nose…
"Tanjiro~! You forgot about me! Waaaaah… Are you abandoning me?" A yellow blur suddenly lunged forward, clinging to Tanjiro's thigh, sobbing uncontrollably. It was Zenitsu.
"Zenitsu~ Don't be like that, it's so unsightly. We'll all train together later, you won't be left out…" Tanjiro said, exasperated, as he wiped snot off his trousers.
Seeing this, everyone burst into laughter—
"Hahahahaha......"
After a day's journey, the train slowly pulled into the station. The [Mugen] train, which had just been repaired, was now completely wrecked. Fortunately, all the passengers on board were unharmed.
Well, not entirely. A few, deluded by Nightmare's (Enmu's) dream illusions, had become assassins driven by dream addiction. Uchiha Nagi had killed them directly. One of them had been killed by the Flame Hashira, who had snapped the person's neck when he sensed imminent danger to his own body.
Among these people's mental worlds, Tanjiro's was the most bewildering. Faced with an assassin sent to kill him, his mental world had eagerly guided the assassin to his spiritual core…
In contrast, the not-so-normal Inosuke and Zenitsu had spiritual cores that turned the tables, treating the assassins like toys. They were truly formidable to the extreme.
On the return journey by rail, they encountered no more demons. The trip was peaceful. The stab wound in Tanjiro's stomach had healed by about eighty percent. Only the Flame Hashira's body still needed time to recover. After all, the blow that pierced his chest had been too severe; he had nearly kicked the bucket. Even if the external wounds healed, internal injuries wouldn't recover in a single day.
Now, Rengoku Kyojuro would cough from time to time. This was because that penetrating strike had injured his lungs. Although Uchiha Nagi had used Medical Ninjutsu to treat his lungs several times, some underlying damage remained. Ultimately, Uchiha Nagi was merely a medical Jonin, not a top-tier medical master like Tsunade.
"We're finally off the train! We can go back to the Butterfly Mansion, that's great~" Zenitsu stretched. "Naho-chan, Kiyo-chan, Sumi-chan, I'm coming for you~~"
"Then Nezuko-chan is mine~" out of nowhere, the little boar, Inosuke, shouted.
"What~ You bastard, Nezuko-chan is mine—" Cowardly and afraid of death, only girls could make Zenitsu never back down.
"You damn pig, what do you need so many for? Are you going to eat her?"
"Ptooey, ptooey, ptooey! Only a demon would eat someone! Wait, no, I won't eat her~"
"@!#￥￥@~!…"
"·"@!%￥%@........"
"Hey, I'm saying, can you two please stop arguing~" Tanjiro said helplessly.
"Hahahaha~"
As soon as the group disembarked, they were met by a Corps member sent to pick them up: Murata, the man rumored to have the strongest luck of any side character, who somehow never died no matter what happened.
"Everyone, please get in the car~" Murata smiled.
To accommodate the injured Flame Hashira, the Demon Slayer Corps had actually dispatched a car this time. Yes, cars existed in this world. Buses, cars, and trains were all present, even guns…
The Wind Hashira's younger brother, Shinazugawa Genya, used a gun.
Of course, aside from powerful explosives, bullets from firearms merely created small holes in demons. Unless their necks were severed by a Nichirin Blade, they had no other weaknesses.
"Oooh, what a huge steel monster! It moves on its own?!" Inosuke tapped the bus-sized vehicle with his sword…
"Inosuke, don't be an idiot! Don't break the car…" Zenitsu covered his head and pulled him into the vehicle.
Uchiha Nagi sat in the front, looking at the familiar steering wheel, accelerator, brake, and other controls. He sighed. Though it looked similar, this ultimately wasn't the world he was born in.
Only Tanjiro, with his dog-like nose, sniffed the air nearby, wondering why Uchiha Nagi was exuding a sense of nostalgia for the past…