When Tomioka Giyu opened the bamboo tube, the chill of the snow still lingered on his fingertips.
A black crow perched on the eaves, tilting its head as it preened its feathers, clearly waiting for his response.
The letter inside was written on thin paper. The handwriting—slightly shaky yet gentle and steady—was unmistakably that of Ubuyashiki Kagaya.
"Giyu, the matter of Hieda Town has been fully understood."
"The tyranny of the officials did not arise overnight, yet the suffering of the people cannot be ignored. Though the Ubuyashiki family does not directly interfere in worldly affairs, we can still make use of certain connections."
"I have ordered my retainers to meet with the lord of the Echigo domain, explaining that the villagers of Hieda Town wish to work under the Ubuyashiki family's workshop, offering their craftsmanship in place of taxes."
"The workshop will mainly produce bamboo crafts, wooden clogs, and leather goods. All products will be sold through the Ubuyashiki family's channels. This will ensure the villagers can live without worry, pay their due taxes, and no longer depend on demons or fear the officials' cruelty."
"The duty of the Demon Slayer Corps lies not only in slaying demons but also in protecting people. To protect their lives is to protect their hearts as well. Do not let hardship make you doubt yourself. What you have done is right and just."
Giyu's fingers tightened slightly around the letter, the edges wrinkling under his grip.
He had expected Oyakata-sama to perhaps warn the local officials in secret—but not this. Not taking the entire village under the Ubuyashiki family's protection.
In this way, the villagers would have stable work, fair taxation, and no need for demonic "protection."
The problem had been solved at its root.
"Please thank Oyakata-sama for me," Giyu said softly to the crow, a faint loosening in his voice.
The crow gave two sharp caws, as if saying, "Understood," before flapping its wings and soaring toward headquarters.
Giyu folded the letter carefully and tucked it close to his chest.
The heaviness he'd carried since the Hieda Town incident finally began to ease.
Oyakata-sama was right—protecting people meant more than killing demons. It also meant giving them hope to keep living.
He turned and went inside, fastening his Nichirin Sword to his back.
With Suzuki Jiro nearly recovered and able to manage the base, and his patrol of the Echigo region complete, it was time to visit that mountain once again.
The forest around the Kamado family home looked far livelier than it had a month before.
The snow had mostly melted, revealing dark brown soil beneath. Fresh green buds dotted the branches, and the air carried the damp, earthy scent of early spring.
When Giyu reached the wooden house, he saw Kamado Tanjuro sitting on the porch, carving something with a small knife.
The sunlight touched his graying hair, giving it a soft golden sheen. His breathing, though shallow, was steadier than before.
"Tomioka-san," Tanjuro greeted with a calm smile. "You came at just the right time. Tanjiro just finished drying the herbs. I'll have him brew some hot tea."
Giyu sat beside him, his gaze falling on the block of wood in Tanjuro's hands.
It bore the shape of a human figure—arms extended, posture fluid, full of rhythm and grace.
"You're carving Hinokami Kagura?"
"Yes. I want to leave something behind for the children."
Tanjuro set down the knife, coughing twice before continuing. "After you left last time, Tanjiro kept asking how your dance practice was coming along."
At the mention of training, Giyu's expression grew more focused. "It's progressing."
For the past month, he had spent nearly every day refining the forms of Hinokami Kagura.
From awkward, stilted movements at the start, he had reached a point where he could string together the first two forms fluidly. Now, he could even shift naturally between Water Breathing and Sun Breathing mid-battle.
The golden glow of the blade appeared more often, and its effect against demons grew stronger.
During his last mission in Hieda Town, when he cut down that multi-armed demon, he had clearly felt the power of Sun Breathing flow through the blade—slowing regeneration and burning the demon's flesh from within.
But he had hit a wall.
"It still feels like… something's missing."
He spoke carefully. "The power of Hinokami Kagura—it doesn't feel complete. Like there's a thin veil between me and it. I can see the shape, but I can't grasp the core."
Tanjuro lifted the knife again, drawing a curved line across the wooden figure. "And what do you think the core of Hinokami Kagura is?"
"The power of the sun," Giyu replied without hesitation. "A pure force that destroys darkness."
"That's right."
Tanjuro nodded slowly. "But the sun doesn't stay in the sky forever. It rises and sets, strong and weak. The midday sun melts snow, but the dawn sun only brings a little warmth."
He looked toward the ridge in the distance. "Hinokami Kagura is the same. Its strength depends on your state."
"State?" Giyu repeated.
"Mm."
Tanjuro tapped the wooden block lightly. "When I was younger, whenever I danced the Kagura, I would feel my whole body heat up, my heart pounding like a drum. In that moment, my strength peaked—my movements were the smoothest. Later, when my health failed, that heat came less often… and the dance lost its power."
He turned to Giyu. "Tomioka-san, when you practice, have you ever felt your body heat up?"
Giyu froze for a second.
He had.
Not only that—it was distinct.
Especially when performing the Second Form: Clear Blue Sky, he could feel his body temperature rise, his blood boiling in his veins, his heartbeat surging.
In those moments, the blade's light grew brighter, and his strikes hit harder.
He had always thought it was just the natural strain of intense breathing.
"Yes," he said quietly.
Giyu spoke in a low voice.
"When I perform Hinokami Kagura, my body heats up, my heartbeat quickens, and my strength increases with it."
"That's it."
Tanjuro smiled faintly. "Hinokami Kagura is a dance that burns life itself. The more you commit to it—the closer you push yourself to your limits—the stronger it becomes. My father used to say that every generation of Kamado men gets a fever while dancing. The higher the fever, the smoother the movements."
A fever…
The thought struck Giyu instantly—words from Tanjiro in his past life.
Back then, Tanjiro had already mastered Sun Breathing. He once said casually, "Every time I use Hinokami Kagura, my whole body feels burning hot, like I've got a fever. Especially when I really do have a fever, my breathing flows easier and the power feels overwhelming."
He hadn't thought much of it then, but now, it made perfect sense.
Increased body temperature, rapid heartbeat… perhaps that was the key to unleashing the full strength of Sun Breathing.
He thought of the marks.
Those mysterious patterns that had appeared during the Infinity Castle battle—awakened by nearly every Hashira.
According to legend, when the mark awakens, the body temperature rises beyond 39 degrees, and the heartbeat exceeds 200 beats per minute.
Marked swordsmen possess power far surpassing ordinary humans—strong enough to stand against the Upper Moons.
In his past life, Giyu himself had reached his peak only after his mark had appeared.
Could it be that the true essence of Sun Breathing is deeply connected to the Demon Slayer Mark?
Tanjuro's "body burning up," Tanjiro's "breathing better during fever"—both could be signs of nearing that same awakened state.
Giyu's breathing quickened.
He recalled how he'd felt when using Sun Breathing—the warmth spreading through his limbs, the pounding in his chest. His body temperature had reached about 37 to 38 degrees, his pulse around 150 beats per minute.
Close… but still far from 39 degrees and 200 beats.
That small gap—that single breath of distance—was what kept him from grasping the core of Sun Breathing.
"Tomioka-san?"
Tanjuro noticed his stillness and asked gently, "Something wrong?"
Giyu blinked and steadied his voice. "No. I just… realized something."
He rose, bowing deeply. "Thank you, Kamado-san, for your guidance."
Tanjuro waved a hand and picked up the carving knife again. "Guidance? Hardly. Everyone sees the Kagura differently. As long as you find your own path, that's enough."
Giyu didn't reply. He turned and stepped into the courtyard.
The sunlight was warm and clear. He drew his Nichirin Sword and took the opening stance of Sun Breathing.
This time, he didn't try to control his breathing too tightly. Instead, he allowed his focus and emotion to merge, letting his strength flow freely.
"Sun Breathing, First Form: Dance!"
The blade flashed—its golden light brighter than before.
He could feel his body temperature rising, his heartbeat pounding, his blood roaring in his ears.
37.5 degrees.
160 beats per minute.
His power had increased—but it still wasn't enough.
"Sun Breathing, Second Form: Clear Blue Sky!"
He slashed again, channeling everything within him—forcing his energy toward the edge of exhaustion.
The blade cut through the air with a heat so intense it shimmered, a faint crackling sound bursting in its wake.
38 degrees.
180 beats per minute.
The golden arc of light almost solidified, striking a wooden post nearby. The wood split in two, the surface blackened and smoking.
Giyu sheathed his sword slowly, chest heaving.
Sweat rolled down his temples and hit the ground—evaporating the moment it touched.
He could feel it now. Just one more step—just a little higher temperature, just a little faster heartbeat—and he could reach that threshold.
That state of 39 degrees and 200 beats per minute.
The mark.
So that was it.
Sun Breathing wasn't a technique without conditions—it demanded extreme ones.
To wield the true power of the sun, the user had to push their body to its limit, to the brink of the mark's awakening.
The Kamado family, perhaps, were born closer to that state—able to inherit Hinokami Kagura naturally.
For others, it required tremendous effort—and painful sacrifice.
Giyu looked down at his hand, the skin reddened from the strain.
He wasn't there yet.
Forcing his body any further would only cause harm.
But now, at least, he knew the way forward.
His future training couldn't just refine technique—it had to strengthen his body until it could withstand greater heat, greater rhythm, and endure the near-breaking pulse of that "extreme state."
Maybe then—when he could hold that 39-degree fever and 200-beat rhythm—he would truly understand Sun Breathing.
Maybe then… he could become the first to awaken the mark.
Giyu took a deep breath. The scent of grass and sunlight filled his lungs, clearing his thoughts.
He looked toward the house, where Tanjuro still sat under the eaves, carving quietly as sunlight bathed him in a calm, gentle glow.
"Thank you," Giyu murmured again—this time to himself.
Then he turned and walked away from the yard, his steps firmer than before.
Less than a year remained before Kocho Kanae's death.
Just over two years before the Kamado family tragedy.
He didn't have much time left.
To grow stronger. To awaken the mark. To master Sun Breathing.
Each step had to be taken quickly—without hesitation.
His figure disappeared into the forest, sunlight streaming through the branches, scattering across his path.
Behind him stretched a long, gleaming shadow—like a trail of light that refused to fade.
His battle had only just begun.