Night settled softly over the Swordsmith Village, the air warm and still. Above the treetops, Akira's tree house loomed like a living tower, its wooden walls glowing faint amber from the lanterns inside.
At the base of the tree, near the clearing where the earth flattened into a training field, Akira stood alone, holding two Nichirin swords. Broken Nichirin blades lay scattered around him like fallen petals.
Akira took a deep breath and activated his Star Breathing.
A sharp pulse of purple light rippled through the clearing as the twin Nichirin katanas in his hands ignited, glowing a brilliant purple. The air trembled faintly from the energy output.
He held the stance, muscles steady, expression firm.
10 seconds.
20 seconds.
30… 40… 50…
By 60 seconds, a faint, ominous crack, like glass shattering, echoed through the still night.
CRACK—PING—!
Both glowing katanas ruptured at once, exploding into fragments that rained harmlessly to the ground, joining the graveyard of broken blades at his feet.
Akira sighed. "…This one is a bust too."
He crouched and picked up a shard of the nearest broken sword, turning it between his fingers. The quality of the metal was identical to Tanjiro's Nichirin, forged with utmost care.
And yet.
"Well," he muttered, "at least this one lasted a full minute. That's a new achievement."
Akira brushed dust off his hands, preparing to gather the latest pile of shattered steel, when a familiar voice drifted from behind him.
"Akira, are you still testing those swords?"
He turned to see Erika stepping out of the tree house, lantern light brushing her golden hair, casting her blue eyes into gentle focus. She approached the clearing, gaze slowly traveling over the battlefield of metal fragments.
"Geez…" she sighed. "I just cleaned this this morning. How many swords did you break today?"
Akira scratched his cheek, looking only slightly guilty.
"Just four. Well, four pairs. So eight."
Erika glared at him.
"You're cleaning this. If you forget, I'll have to… I don't know… punish you somehow."
For a split second, Akira almost asked how?
But survival instinct finally kicked in, and he chose life.
"O-okay. I'll clean them. I promise."
Erika exhaled tiredly as she looked at the mess.
"So none of them worked today either?"
"Nope," Akira admitted. "But the last one lasted a whole minute."
"I don't get why they always break." She asked.
Akira explained. "Well, it's because of the special properties of scarlet iron ore. It conducts energy better than any other metal. A normal Demon Slayer's energy output isn't that high, so Nichirin blades work fine. But my Star Breathing's output is way higher than anything a Nichirin blade is designed to handle."
He nudged a broken shard with his foot.
"If the blade were as big as my Demon Slayer sword, maybe it could last longer. But normal-sized katanas just… explode."
Erika folded her arms. "Then why not focus on the big one? And adjust your forms for that?"
Akira gave a stubborn shrug. "No, I want to dual-wield."
"…Why?" Her stare sharpened accusingly.
"Because…" Akira straightened with absolute seriousness.
"…dual-wielding katanas is cooler."
Erika looked at him as if wondering how someone could be this intelligent and this stupid at the same time.
Akira quickly raised his hands.
"Not just that! Upper Moons are fast. Big swords slow me down. Twin katanas are better for agility."
"Mm-hm," Erika muttered, clearly unconvinced. "Whatever. But you're still breaking all the swords. What are you going to do?"
Akira sighed.
"I don't know. Scarlet iron just isn't strong enough."
Erika thought for a bit and said.
"Why not make an alloy with titanium or other strong metals?"
"Because any more impurities will reduce energy conduction," Akira replied immediately. "It might make the sword stronger, but it won't kill demons as effectively."
He sighed. "If I had some magic metals like adamantite or orichalcum, or mythril, it might work. But none of those exist in this world. And I also can't use the magic metals I brought."
He sighed again, shoulders slumping under the frustration.
Erika sighed with him.
"Too bad you can't use your evolution power on inorganic things," she muttered. "Otherwise, you could've just… evolved the swords stronger."
She expected Akira to laugh it off, maybe say something like "Haha, metal can't evolve."
But instead.
Akira froze.
His eyes widened.
His entire expression shifted from confusion… to realization… to horror that he hadn't thought of this earlier.
"…inorganic evolution… why didn't I think of that…? How did inorganic beings evolve anyway…"
Erika immediately regretted everything.
"What have I done…?"
She genuinely couldn't tell if she had just solved his problem… or unleashed something catastrophic.
She tried ignoring Akira, entering full genius-mode, muttering, and instead looked at the forest, the mountains, and the starry sky. Fireflies drifted lazily around them.
These past months have been peaceful.
Just the two of them living together in the tree house away from the village, sure, it's chaotic… but it's still peaceful.
She wanted it to last.
Without thinking, Erika whispered, barely audible:
"…Can we just stay like this forever, just the two of us?"
The moment the words left her mouth, her eyes widened.
"…Did I just say that out loud!?"
Akira stopped muttering and stared at her, eyes wide in surprise.
Their eyes met.
The air thickened.
The fireflies drifted more slowly.
The world seemed to pause.
Akira opened his mouth to say something, but.
BEEP—BEEP—BEEP—BEEP—!!!
A loud alarm shrieked through the night from inside the tree house.
The peaceful moment was shattered instantly.
Akira's expression hardened instantly.
"That's the demon-sensing alarm," he said, already turning toward the village. "They're near. They've found this place."
These alarms were the same sensors he built into Yoriichi Type Null, small devices planted throughout the forest, attuned to detect demonic energy. Akira had scattered dozens of them around the Swordsmith Village, fully expecting the climax of this arc to arrive soon.
Erika's eyes widened.
"What should we do?"
Akira didn't hesitate.
"We regroup in the village and form a plan of attack. Good thing I placed alarms in the village too, so the villagers should've heard the alarms too; they're probably panicking already."
They grabbed their equipment and sprinted toward the village.
"By the way, did you hide the tree house?" Akira asked.
Erika nodded, breath steady. "Don't worry. I already did.
Erika used her blood demon art she copied from Yushiro, Blindfold, to make it disappear. Though she can't hide the entire village, since it's way too big."
By the time they reached the Swordsmith Village, it was already in full emergency mode, and chaos had already erupted.
Lanterns swung wildly.
Masked smiths scrambled through the streets.
Families huddled together as emergency horns blared through the night.
They spotted Tanjiro, Nezuko, and several villagers gathered around the village chief.
Tanjiro turned the moment he sensed them.
"Akira-san!!"
He rushed toward them, relief mixing with urgency in his voice.
Akira and Erika reached Tanjiro and Nezuko, who were already gathered with a small group of masked smiths, demon slayers, and the village chief, and the Ameri….Genya stood there too, looking irritated as always.
"Ah, right… Genya," Akira thought. "Almost forgot he exists. Good thing I made him that better gun."
Everyone turned to Akira.
"Akira-san! What should we do?!" someone asked.
Panic laced their voices.
Akira took command immediately.
"First, the villagers stay here with the Demon Slayers. Protect the center of the village. The rest of us will head out and defeat the demons."
He scanned the group.
"Where's Mitsuri?"
The chief replied quickly, "She is nearby. She will be here soon."
Akira frowned slightly.
"Muichiro is not here this time… so the only Hashira close enough is Mitsuri".
But he wasn't too worried.
"Upper Moon Four and Upper Moon Five, they're easy if you know where their cores are. We've got this".
The chief swallowed hard.
"Hoshino Akira… how strong are these demons? Should we deploy the Yoriichi Type Nulls?"
Akira shook his head.
"No. Not yet. They're for the Upper Moons and Muzan. If Muzan learns about them now, it'll be bad".
Akira knows they can handle Upper Moon 4 and 5 without revealing all our cards, but he had to know their location to prepare a plan of attack.
"Erika," he said, turning to her, "we need aerial surveillance."
Erika nodded at once.
Akira called their kasugai crows, Raven and Rose
The two birds swooped down. Erika tapped talismans on their heads.
Raven cawed, "aerial surveillance! aerial surveillance!"
Rose cawed proudly, "Leave it to us! Leave it to us!"
The crows cawed and flew into the sky.
Erika activated vision-sharing, as Akira saw the forest from the sky with his mystic eye of Truth.
There, he could see the demonic energy of the upper moon's level, one, two… and three?
"Why were there three of them?" Akira thought, then he recognized one of their energy signature immediately. "…what the hell is he doing here?"
Upper Moon Three — Akaza.
Selena's voice rang in his head.
"Brother, you changed too many events already. This is inevitable."
Akira sighed.
"…this is going to be a bit difficult."
He opened his eyes.
"There are three Upper Moon demons. Plus several normal demons, though the weaker ones seem to share identical signatures, so they are probably one of the Upper Moon's Blood Demon Arts."
The entire group went pale; they did not expect three upper moon demons to attack them all at once.
Akira continued.
"Erika, Tanjiro, Nezuko, and Genya, you four take Upper Moon Four. When Mitsuri arrives, tell her to join you."
Erika steeled herself.
Tanjiro nodded firmly.
Nezuko clenched her fists.
And Genya cocked his gun with a click, trying to look cool.
Akira continued.
"The rest of the Demon Slayers stay here and protect the village from normal demons."
He turned to the swordsmith chief and pointed toward the forest.
"Activate Yoriichi Type Null Alpha. It can handle one of the Upper Moons alone."
The chief asked,
"Just Alpha? Should we deploy more?"
Akira shook his head. "No. We can't reveal everything yet. Keep the others hidden. They are need to stay here for emergencies. Alpha is strongest anyway."
He lifted his head.
"So is everyone okay with the plan?"
Everyone nodded with steely determination.
Just before the group split up, Akira raised a hand.
"Oh, before you go. Nezuko, eat this."
He flicked a small, round pill toward her with perfect accuracy.
Nezuko caught it mid-air, blinking curiously.
Tanjiro leaned forward.
"Akira-san… what is it?"
Akira answered casually, as if he weren't handing a demon girl a mystery drug.
"Just some medicine. It'll help her stay in control… among other things.
Just eat it."
Nezuko stared at him for half a second.
Then, chomp.
She swallowed it without hesitation.
Tanjiro nodded. After everything they'd been through together, both siblings trusted Akira completely.
Akira turned to Erika.
"Erika," he said softly but firmly, "be careful, and don't show them any mercy."
Erika nodded, matching his seriousness.
"You be careful too."
Their eyes met for a brief moment, silent understanding passing between them.
Then everyone moved.
Tanjiro, Nezuko, Erika, and Genya dashed toward their assigned battlefield, their opponent is Upper Moon 4—Hantengu.
Demon Slayers formed defensive lines around the village.
Nearby, a Yoriichi Type Null unit activated. Its eyes glowed red.
Yoriichi Type Null: Alpha, the very same machine that had somehow cured Muichiro's amnesia, marched forward with mechanical determination.
Its directive was simple.
A single-line command burned into its core.
Track 'em, Find 'em, Kill 'em.
Without hesitation, Alpha split off, heading toward the other demonic signature Akira had assigned to it.
The earth trembled with its heavy metallic strides as it sprinted into the forest, ready to destroy the Upper Moon 5—Gyokko.
Akira ran the opposite direction, toward a crushing wave of killing intent.
He ran through the forest alone, branches tearing in his wake, the wind cutting against his skin.
He could feel the presence approaching, violent, overwhelming, familiar.
A figure burst through the treeline at the exact same moment.
Upper Moon Three.
Akaza.
Their eyes locked.
Akaza grinned, overflowing with battle hunger.
"Akira… finally. We can fight."
He didn't wait.
He charged, the forest exploding beneath his feet.
Akira grinned right back.
"Ohh? Too eager for a rematch? Let's end it here."
They both punched, as their fists collided.
BOOOOOOM—!!
The shockwave tore through the forest, uprooting trees, shattering stone, and splitting the night sky with raw force.
The real battle had begun.