Tanjiro did not hide his encounter with Hiru. He recounted everything in detail to Tanjuro.
"Hmm… I see. Ahem."
Tanjuro frowned.
"Unless absolutely necessary, stay off the mountain for now. Put those medicines away too…" He coughed heavily.
"I understand… but Father, that man truly harbors no ill will." Tanjiro raised his hand to help Tanjuro steady his breathing. "Why are you so wary of him?"
"Tanjiro, some things aren't as simple as they seem. But knowing that he has no immediate malice is enough…" Tanjuro coughed softly again. "I wonder how much time I still have to teach you…"
"What are you going to teach me, Father?"
"Breathing."
Tanjiro looked confused. "But I breathe all the time?"
"Not that kind of breathing, but another kind—a way of breathing that unlocks your true potential."
Tanjuro frowned and paused to compose himself before continuing.
"I originally had no intention of teaching you the Breathing Styles. Using them is equivalent to overdrawing one's own potential—borrowing strength from heaven that must eventually be repaid. My current condition is partly the result of having used the Breathing Styles."
"Then please don't use the Breathing Styles anymore," Tanjiro said anxiously. "If you keep using them, your body will just continue to deteriorate."
Tanjuro reached out and ruffled his son's hair, smiling gently.
"No. I've always been weak to begin with. This is simply my original state, revealed after I stopped using the Breathing Styles. If anything, I should be grateful to them. It was because of the Breathing Styles that I was able to live like a normal person and spend so many years with all of you."
"Father…"
"Tanjiro, promise me this." Despite his sickly appearance, Tanjuro's gaze was still filled with pressure.
"If you manage to learn the Breathing Styles, then unless it is a moment of life and death, you must never use that power. I can sense that the strength gained through the Breathing Styles is not the end. There are higher realms beyond it. But although those realms may be attainable, they exact an enormous cost from the body. I want you to have strength, but I do not want you to harm yourself in pursuit of it."
Sensing the seriousness in his father's words, Tanjiro straightened. "Yes. I understand. I will never misuse this power outside of protecting everyone."
"Good. Then listen carefully to what I'm about to tell you."
Tanjuro coughed lightly.
"The essence of the Breathing Styles is to rapidly inhale a large amount of air in a short time, then guide it through the lungs to accelerate the circulation of blood throughout the body, allowing you to gain greater strength and speed.
"As long as you maintain the correct breathing rhythm, continued movement will not be difficult. Your vitality, energy, and spirit will be replenished through breathing, allowing you to act for days on end without collapsing from exhaustion. But this lack of fatigue is only superficial. In truth, the body is being excessively strained.
"That's why, in order to prevent the Breathing Styles from overtaxing your body, physical training is also essential. The stronger your physique, the less burden the Breathing Styles will place on you. So starting tomorrow, Tanjiro, if you are to properly shoulder this power, you must work even harder to train your stamina."
"Yes!"
"I know you've always been a dependable child…" Tanjuro smiled, though the expression carried a bitter resignation. "I'm sorry. I lack the ability to resolve everything myself, and instead end up forcing you to bear all of this."
"No, I'm happy if I can help." Tanjiro shook his head. "But I still don't really understand how to breathe properly… When you say to inhale a large amount of air, do you mean deep breathing?"
"Not deep breathing. It's about taking in as much air as possible. Remember to tighten your abdomen…"
Tanjiro listened attentively to Tanjuro's explanations and began training the next day exactly as instructed. His physical conditioning progressed smoothly, but when it came to the Breathing Styles, his progress was far from ideal.
Tanjuro only told him not to rush, advising him to put more effort into sensing the changes in his own body.
During this period, every time Tanjiro returned from going down the mountain, he would smell Hiru's scent. Yet no matter what he said, Hiru never showed himself again. It was not until the beginning of the New Year, when the Kamado family began preparing for their annual deity festival, that Hiru paid another visit.
This time, however, he had restored his original appearance, startling everyone except Tanjuro.
Dressed in ceremonial attire and gripping the ritual implements in his hand, Tanjuro motioned for his family to step back. He advanced a few steps, frowning as he looked at Hiru.
"What are you here for this time?"
"Hey now, no need to be so tense." Hiru stepped back in response, raising his hands to show he meant no harm. "I just want to see the Kagura dance that's been passed down. You know what it originates from, after all."
"…Don't come near my family."
"Alright, I'll stay here and watch." Hiru retreated a few more steps. "But once I'm done watching, I'll really leave. Are you truly unwilling to reconsider my proposal?"
"There's nothing to consider."
"…I see."
Hiru lowered his gaze.
"Then remember to stay vigilant. I'll write to the master about the situation here. There may be members who come to make contact with you."
Tanjuro frowned. "That won't be necessary."
"Don't refuse so quickly. If it's a physician, at least let them examine you. They're quite skilled at recuperation." Hiru waved at Tanjiro behind him, who was looking on with concern, signaling that everything was fine. "Think of it as doing it for the sake of spending more time with your family."
"…What exactly is your purpose?"
"Didn't I tell you from the very beginning? You just didn't want to believe me."
Tanjuro fell silent for a moment before speaking again. "Those medicines—what are they for?"
"For killing demons."
Watching the change in Tanjuro's expression, Hiru sighed.
"Yes, yes, I know. A demon carrying demon-slaying medicine makes no sense, right? Honestly, I didn't think that far back then. By the time I came to my senses, things had already turned out this way. Sometimes, even I don't want to believe it myself."
Tanjuro: "…"
"And besides, look—I haven't done anything to you these past few months, have I?" Hiru spread his hands. "If anything, I cleared out some bears and wild boars in the mountains because I was hungry. I even saved you a bit of trouble."
Tanjuro closed his eyes briefly. "…If you're hoping to persuade me with something like that, you'll be disappointed."
"Haha, I already gave up on making you believe me." Hiru shook his head. "If it weren't for humans coming instead, just getting you to lower your guard would be difficult. Maybe having someone who knows the truth talk to you would work better—though I suspect if my brother came, you'd be able to communicate with him properly."
"If all demons were like you, I wouldn't mistake them."
"That's not what I meant… But I can confirm that among demons like me, the only one of my kind is Muzan."
Tanjuro frowned slightly. After a brief silence, he turned and walked toward the area prepared in advance.
"If I have enough time, I'll see it for myself."