Xiao Hei wore a mischievous grin on his face.
"Tanjiro, the next rule is simple. You must always maintain your Total Concentration Breathing, and endure both Xiao Bai and my attacks. During this time, you can dodge, but if your breathing falters, you'll have to face your master's punishment."
Tanjiro nodded and glanced toward Feng Yu, who was sipping tea nearby.
"Don't worry about me. Just focus on your training," Feng Yu smiled reassuringly.
Then, from behind, he pulled out a large wooden stick, bigger than a fist, and placed it by his feet.
"Oops, sorry. Didn't mean to let you see that…"
Tanjiro: "…"
Taking a deep breath, Tanjiro cleared away the painful memories in his mind and steeled himself. "Let's do this!"
"Gah gah! Then let's begin!" Xiao Hei called out.
With that, Xiao Hei soared into the air, his massive wings flapping faster and faster. A violent gust of wind rushed toward Tanjiro.
Where the wind passed, dust and stones flew. Meanwhile, Xiao Bai stood to the side, gathering energy balls to attack Tanjiro.
The intense wind caught Tanjiro off guard, sending him crashing into a tree trunk.
"Ugh!"
Tanjiro felt a sharp pain shoot through his body, and in that moment, his Total Concentration Breathing faltered.
"Your breathing faltered…"
Feng Yu quietly picked up the wooden stick and, with a grin, walked toward Tanjiro.
"Ah!"
Tanjiro's scream echoed into the sky.
"Continue," Feng Yu said quietly as he sat back down.
Struggling, Tanjiro got up and resumed his Total Concentration Breathing, dodging the attacks from Xiao Hei and Xiao Bai.
However, this time, Xiao Bai didn't release energy balls like before. Instead, three tails shot toward Tanjiro with incredible speed. He didn't react in time to dodge.
Once again, Tanjiro was sent flying.
Feng Yu silently stood up, holding the wooden stick…
Thus, the entire day passed, with Tanjiro enduring relentless attacks.
Every time he collapsed, Feng Yu would silently take out a healing pill and feed it to him.
Then the next round of torment would begin.
On the other side, Nanako was climbing the mountain with Sakonji Urokodaki. As they neared the summit, the air grew thinner.
Sakonji's breathing remained steady, but Nanako's face grew red as her breaths became more and more labored.
"Master Sakonji… How much further?" Nanako asked.
"Almost there," Sakonji replied calmly.
"If you can't even handle this environment, you don't deserve to become a Demon Slayer, nor do you have the resolve to avenge your mother!"
Nanako's expression immediately darkened, clearly upset.
"Your master, Feng Yu, and Tanjiro went through this too. They are much more outstanding than you. Do you realize how pathetic you're acting right now?"
"With your greenish eyes, exceptional speed, and quick reflexes, you should not be acting like this!"
"Nanako, summon your inner courage. Think about how your mother was killed by demons. Think about how they tore her apart, bit by bit, and how they discarded her afterwards!"
Each word from Sakonji seemed to jab at Nanako's nerves.
"Enough!" Nanako shouted.
"I… I'm not useless!"
She bit her lip, fighting the discomfort in her body.
Sakonji turned around and calmly looked at her.
He noticed her lip was bleeding from where she had bitten it.
"Good. You have the resolve to be a Demon Slayer, but resolve alone is useless. Next, I'll test if you truly have what it takes to become a swordsman."
Sakonji's voice grew heavier as he continued walking.
Nanako followed quietly behind him, but the air grew thinner, and with each step, her pace slowed. She had to stop every few steps to catch her breath.
"My lungs hurt… My head's spinning…" she muttered.
But remembering Sakonji's earlier words, she pushed through, determined to keep going.
Soon, Nanako found herself falling behind Sakonji.
"Hey, Master Sakonji, where are you?" she called out.
The towering pine trees swayed violently in the wind, producing eerie "rustling" sounds.
As the trees swayed, blocking the sunlight, Nanako realized that what had been an already dim forest had turned pitch-black.
"Sakonji… Master Sakonji… where… where are you?"
She called out again, but only the sound of dry branches falling around her answered.
"Ah!"
Nanako screamed in fear.
After a moment of panic, she realized it was just a dry branch…
"Am I really… this useless? Scared by a mere branch…?"
"If I'm like this… how can I avenge my mother?"
Powerlessly, Nanako sank to the ground, tears falling endlessly.
"Mother… What should I do?"
She was like a frightened deer, curled up beneath a tree, covering her ears and crying.
The severe lack of oxygen made her dizziness worse, and her vision blurred.
Everything around her seemed to quiet down. She could almost hear her own heartbeat—slow but steady.
"Child…"
Nanako's eyes snapped open, and tears streamed down her face.
"Mother!"
She threw herself at the vision of the woman and cried out.
"Child, you've done well… I've always been with you… so don't fall here!"
The figure of Nanako's mother faded away, and Nanako opened her eyes again. Her gaze was blank as she stared at the spot where her mother's image had disappeared.
If Feng Yu had been there, he would have noticed that the green in Nanako's eyes had deepened.
She didn't know how much time passed, but then Sakonji's voice cut through her thoughts.
"Catch up."
Nanako looked up to see Sakonji, wearing his tengu mask, standing ahead.
"Ah, still not quite there…"
"But you're young, and for you to make it this far is already impressive," Sakonji reassured her.
Nanako wiped her tears away, stood up, and quietly followed him, her breathing much steadier now.
Sakonji noticed the change in her but said nothing, continuing his walk.
Finally, he stopped and turned to face Nanako. "This is it. You need to make your way back to the cabin before nightfall."
Nanako wanted to say something, but just then, a gust of wind blew past, obscuring her vision. When the wind calmed, Sakonji's figure had vanished.
"Go back…?"
She turned around to face the path they had come, but now all traces of it had disappeared, leaving only unfamiliar terrain.
"Mother… I will… I will make it…"
Nanako clenched her fists, determination burning in her eyes.
Hidden in the shadows, Sakonji quietly observed her. He had never told her that Feng Yu and Tanjiro had made their ascent at night. He considered Nanako's age, but seeing how she was handling herself now, he felt satisfied with her progress.
"She's a good seed…"