"…Are you three really that scared of me?" Yōsuke looked helplessly at the three girls before him, each with round, beady eyes.
These weren't Tanjirō, Zenitsu, or Inosuke, but the Butterfly Mansion's medical staff apprentices: Terauchi Kiyo, Nakahara Sumi, and Takada Naho, who studied medicine under Kanae and Shinobu.
Earlier that day, the three had mistaken Yōsuke for a newly arrived patient of the Demon Slayer Corps. But the moment they faced him directly, an inexplicable fear took hold of their hearts. Trembling all over, they forced themselves to muster the courage to ask where he was injured. When he explained he was the mentor of the Butterfly Sisters, their shaking only grew worse.
Kiyo's hands shook so violently that tea spilled everywhere before she managed to place the cup before him—with barely any left inside.
Yōsuke had already suppressed his presence to its lowest level. Unless one had a sense as sharp as Tanjirō's nose or Zenitsu's ears, it should have been impossible to detect him.
But he had overlooked one thing: the difference between species.
Even a cat, when faced with a sleeping tiger, would instinctively feel fear. Such responses were ingrained in nature itself.
And there was another reason—the weight of being their teachers' teacher. Shinobu, during lessons, was famously strict. Naturally, they imagined that Yōsuke must be even harsher.
Just as the three stood frozen in confusion, their leader's voice called from outside.
"Kiyo, Sumi, Naho—where are you? Training is about to start!"
It was Kanazaki Aoi, searching everywhere for the trio. Since Tanjirō, Zenitsu, and Inosuke had finished their rest, it was time for their rehabilitation training, yet the three girls were nowhere to be found.
To the apprentices, Aoi's voice sounded like salvation itself. They turned their wide eyes toward Yōsuke, hope glimmering within them.
Yōsuke chuckled. "Go on."
Relieved, the three hastily wiped away the tears brimming in their eyes and ran out as quickly as they could.
From outside came Inosuke's roaring voice:
"Kamaboko Gonpachirō! Let's fight!"
"My name is Kamado Tanjirō!" he corrected once again, exasperated by Inosuke's endless misnaming.
Suddenly, the boar's head atop Inosuke twitched. "This feeling… it's Jūmonji Yōsuke! Beast Breathing—Charge!"
He dug his feet into the ground and bolted toward Yōsuke's room.
But Tanjirō lunged and pinned him down just in time. "Inosuke, don't bother Yōsuke-san! And at least remember his name properly—it's so rude otherwise!"
Zenitsu, meanwhile, peeked into the room, but seeing no sign of Yōsuke, promptly began pestering Aoi and the apprentices again.
"They're lively, aren't they?" Tamayo's gentle voice came from beside Yōsuke as she appeared, smiling at the energetic chaos outside.
Yōsuke sipped his tea. "They certainly are. But what brings you here?"
"There are many patients in the Butterfly Mansion. I helped Kanae and Shinobu finish treating the worst of them. They insisted I take a break afterward, fearing I'd overwork myself. Your disciples are remarkable—not only in their skill, but in their character as well," Tamayo explained.
"I'm proud to call them my disciples," Yōsuke admitted.
Watching his profile, Tamayo suddenly felt a strange premonition. "…You're leaving, aren't you?"
"You noticed? Yes. It's about time."
"Won't you stay a few more days? Kanae and Shinobu seem so reluctant to part with you."
Yōsuke smiled softly. "Every farewell is just for the sake of a better reunion."
"Then… when will you go?"
Looking out at the sunlit sky, he answered, "Tonight. If I slip away without saying goodbye to Kanae, Shinobu, and Kanao, they'll surely hold it against me."
That evening, after a long day of tending to the wounded, the Butterfly Sisters and Kanao—fresh from training Tanjirō, Zenitsu, and Inosuke—hurried into Yōsuke's room, eager to see him.
"Master, let's take you and Lady Tamayo out to stroll nearby!" Shinobu suggested brightly.
Yōsuke shook his head. "No. It's time for me to leave."
"What? Already? You've only been here a single day!" Kanae's voice was heavy with reluctance.
Kanao clutched tightly at Yōsuke's sleeve, unwilling to let him go.
He stroked her head affectionately. "I still have my own tasks to complete. But when everything is settled—no matter how long it takes—I will stay with you all."
Shinobu muttered in disappointment, "But I haven't even shown Master around properly yet…"
"There will be another chance. Now, go fetch Tanjirō and the others. I have something to tell them."
Soon, the three boys entered the room. Yōsuke, sensing how much stronger they had become since their last meeting, couldn't help but reflect on how quickly time passed.
"Tanjirō."
"Yes!" Tanjirō sat up straight, awaiting his words.
"You've used the Hinokami Kagura, haven't you?"
"Yes, Yōsuke-san. But… it places an enormous burden on my body. The last time I used it, I was left weak for a long while afterward."
"The Hinokami Kagura is in fact the origin of all Breathing techniques—the Breath of the Sun. Every style stems from it. Long ago, your ancestor Sumiyoshi inherited it directly from Yoriichi Tsugikuni. Your body, however, is still too weak. You lack the stamina to fully wield Sun Breathing forms. So strengthening your body is essential."
"I understand! I'll train hard to build myself up!" Tanjirō vowed.
Yōsuke turned to Zenitsu. "Zenitsu. Your personality is far too extreme—cowardly, pessimistic, timid."
With each flaw Yōsuke named, Zenitsu's head drooped lower.
"…But I can only use a single Thunder Breathing form. That's why I'm so scared…" he muttered.
"So what if you only know one form? Every technique is created by someone. Each style's First Form is the foundation for all the rest. If you've mastered the First Form, you can build upon it and create more. In fact, haven't you already?"
Zenitsu thought back to the Sixfold Thunderclap and Flash he had performed at the Drum House and Mount Natagumo. True, it had only been a way to compensate for the limitations of the First Form…
"Does… does that count as creating a new form?" he asked timidly.
"Of course it does. If all you do is repeat the forms as written, no matter how many you learn, it won't matter. What's important is recognizing your technique's flaws, refining it, and shaping a style that suits you best. Don't dismiss yourself. Sometimes, you must trust in your own abilities."
Zenitsu's eyes lit up. So… I really am amazing after all?!
Finally, Yōsuke turned to Inosuke. "Inosuke."
"Yatako Inrō! What do you—"
Before he could finish mangling Yōsuke's name, both Tanjirō and Zenitsu punched him in the stomach in perfect sync.
"Inosuke! Be polite to Yōsuke-san!" they scolded.
Yōsuke chuckled. "You have great talent. To create your own Beast Breathing is no small feat. Its essence is closest to Wind Breathing. Study it—you can refine your Beast Breathing further. Then you'll become even stronger."
Having addressed all three, Yōsuke encouraged them:
"From here on, your paths are your own. Work hard. I'll be waiting to see how far you grow."