Taking a deep breath of cold air, Tanjiro steadied himself. His hands gently cupped Nezuko's warm cheeks with brotherly affection, and she leaned into his touch without hesitation.
"Nezuko, you know Onii-chan loves you with all his heart, right?" he whispered. Their faces were close enough that she heard him clearly. She nodded, eyes soft.
"Mm… Nezuko loves Onii-chan too!" she said with an angelic smile.
Hearing exactly what he wanted, a smug little smirk formed in his mind.
"Hm… but we need to prove it. No, we should seal it properly right now, or else it feels meaningless," he said, pretending to think deeply.
Catching her curious look, he added, "Right?"
"Um… if Onii-chan thinks so…" she tilted her head.
Damn, she's cute…
Holding back the urge to rub her cheeks, he leaned in slightly. "Then prove your love to Onii-chan."
"Ehh… how?" Nezuko asked honestly, blinking.
He gave her an obvious smile. "With a kiss, of course, silly girl."
A faint blush dusted her cheeks. She nodded, leaned forward, and gave him a small peck on the cheek. "I… I did it…"
"…"
No system notification appeared.
Yeah, that tiny peck didn't do it… Guess the system wasn't satisfied… Looks like I'll have to do it myself.
He let out an exaggerated sigh, shoulders drooping. "Nezuko… that's not how we kiss someone we love."
"... We don't?" she blinked.
He shook his head.
"Then… what's the correct way, Onii-chan?" she asked, genuinely confused.
Oh?
Touching his chin, he explained, "Haven't we seen Mom and Dad kissing when they thought we weren't looking? You remember how they did it with real affection, right? That's how you're supposed to kiss someone you love. That's how you should kiss Onii-chan."
Nezuko's face instantly turned bright red. Her eyes widened in shock and she went quiet.
O-Onii-chan wants that…?
She remembered that moment years ago — her mother embracing their father, lips pressed, tongues moving strangely. The memory had burned itself into her mind.
"Ehh… b-but…" she murmured, cheeks glowing.
He could see her emotions spiraling, and a hint of regret crossed his face.
Not as easy as I thought… but I'm not done yet.
He stepped back and put on an indifferent expression. "If Nezuko can't do it, then I guess Onii-chan has no choice… I'll just find a nice girl in the village and have her kiss me with love instead… sigh…"
He turned as if to leave.
But at that moment, Nezuko grabbed his sleeve.
Tanjiro stopped and looked back. Nezuko was biting her lip, her face redder than ever.
"I… I'll… k-kiss Onii-chan properly this time…" she said, trembling.
She stepped closer, ears and cheeks crimson. Her eyes flicked to his lips, and she nervously licked her own.
For years, she had secretly wondered what a kiss felt like. Sometimes she'd even dreamed about kissing her perfect Onii-chan. And now… it was happening.
Tanjiro saw the resolve in her eyes and smiled softly.
"It's alright, Nezuko. Don't force it. Let me help you."
"Huh?"
Before she finished reacting, Tanjiro's face was already close. His lips pressed gently against hers, his hands holding her head as he kissed her softly.
"Mm…" After a moment of shock, she slowly kissed him back, parting her lips the way she remembered their mother doing long ago.
'Ahh... Onii-chan's tongue... it's inside...'
Nezuko's entire body stiffened the moment she felt it.
Tanjiro, lost in the kiss, suddenly froze as the system notification flashed before his eyes.
[Mission completed!] [You may claim your reward now.]
[Claim] [Later]
A satisfied smile spread across his face. He gently stroked Nezuko's dazed head, his touch overflowing with affection.
"Nezuko's lips belong only to Onii-chan, understand?" he whispered softly. "I have to head to the village now. Go straight home and wait for me, okay?"
He lightly tapped the tip of her nose with his finger, then turned and walked away.
Nezuko stayed silent the whole time. She watched Tanjiro's figure grow smaller and eventually disappear into the distance. Almost unconsciously, her fingertips brushed her own lips; the lingering warmth from moments ago still hadn't faded.
The faint trace of their mingled saliva felt cool against her skin, yet every subtle movement of her tongue brought back the vivid memory of how gently, how lovingly Onii-chan had explored her mouth.
"Onii-chan…" she murmured, her cheeks burning crimson. "Come back soon…"
....
Tanjiro hurried down the path. After a few minutes, once he was sure no one could see him, he flung the charcoal-filled basket to the ground and broke into a wild smirk.
"Can't wait anymore, keke!"
He tapped [Claim] without hesitation.
Instantly a ferocious heat erupted inside him, like he'd been tossed into a raging furnace or, more accurately, chained beside an active volcano spewing waves of molten air.
The burning sensation swallowed him whole in seconds.
He crumpled, knees hitting the snow. One hand clutched his chest as his heart thundered so violently he thought it might burst out of his throat.
OHHH CRAP, WHAT THE FUCK, THIS POWER, FUCK, FUCKKK!!!
He tried to scream, to roar, but no sound escaped.
The agony lasted a full minute before it finally began to fade.
"Ha… ha… haaa…"
He panted hard, each breath turning to mist in the frigid air.
Then a grin spread across his face, too sharp and too hungry to be called a simple smile.
"I feel it. This overwhelming power. It's surging through every part of me…"
He shot to his feet in one jerky motion.
The world had transformed.
Standing still, he could see trees pulsing with life at the microscopic level: sap flowing, cells breathing, nutrients racing in rivers of vivid color he'd never imagined existed.
"Absolutely mesmerizing…"
Beyond that, the living auras of thousands of small animals and even his distant family glowed clearly in his senses.
All thirteen forms of Sun Breathing were etched perfectly into his mind and body, as though he'd practiced them for decades. Total Concentration Breathing had already kicked in on its own, steady and effortless.
His heart settled into profound calm. His spirit flooded with serene, unshakable fulfillment.
He slowly clenched his fist, feeling unimaginable strength coiled quietly within, waiting to be unleashed.
No wonder Muzan was terrified of Yoriichi and called him the true demon...
Tanjiro's lips curved higher.
"This kind of mind-blowing power… it's mine now."
Tanjiro didn't wait another second. He pulled the old family axe from his belt, the one handed down through generations of Kamado men, and the moment his hand closed around the handle he realized just how monstrous his grip had become.
"… Fucking ridiculous."
He swung the axe lightly. The blade cut the air with a sharp whoosh even though he barely used any strength.
Let's try it out...
He stepped toward a nearby tree. The cold no longer bothered him; warmth flowed naturally from his body, and the snowflakes melted before they could touch his skin. His breathing stayed steady, his mind clear and calm.
In an instant he saw the tree's weak points as clearly as if they were marked.
His arm moved.
[Twelfth Form: Flame Dance.]
A clean vertical slash followed by a precise horizontal cut. His stance never shifted.
Crack—!
With a faint snap, the trunk broke where the blade had bitten deep. The thick tree fell with a heavy thud, snow bursting around it.
Tanjiro looked at the smooth cuts and gave a small nod. He had only used a fraction of his strength, yet the ordinary axe had sliced through solid wood like it was nothing.
If this was possible with an axe, what could he do with a real sword?
A Nichirin sword in his hand would surely turn bright red the moment he touched it. He was certain.
Wait… a sword. He still needed one.
His eyes widened slightly.
As if answering his thought, a system panel appeared.
[𖤐 Mission: Practice Sun Breathing for 12 consecutive hours]
[𖤐 Reward: Heavenly Demon Sword]
Tanjiro read the text.
A faint smile tugged at his lips.
"God bless this shit…"