Chapter 9
The earth was cracked from magical pressure. The air, distorted by an invisible gravity.
Zalario, Mystic Admiral in service of Feldway, walked with a slow but unstoppable pace, like an ancient judge delivering his final verdict.
In front of him, Treyni was breathing heavily, her shoulders trembling. A line of golden sap ran down her left side—a clear sign of a deep wound in her abdomen.
Beside her, Charys remained on her knees. Her left arm, already lost, was a stump covered in smoke and evaporated magical blood.
The battle had lasted longer than logic should have allowed.
"…What a waste of time…" Zalario murmured calmly. His voice was crisp, emotionless. "I had no intention of killing unnecessarily. But your stubbornness leaves me no choice."
Treyni barely lifted her head.
"We're sorry… Ramiris-sama gave us no other option."
"And we're not allowed to surrender," Charys added with an empty smile. "I told you we'd die in style, right?"
"…Yes. You did."
They looked at each other one last time. Old comrades. Old friends. Old weapons of a peace that never came.
Zalario slowly raised his arm, gathering energy in his palm.
Then it happened.
A flash. A sharp impact—no magic, no forewarning.
The spatial barrier surrounding Zalario vibrated… and shattered like glass under invisible pressure.
A fine, almost imperceptible cut traced diagonally across his back. Just a scratch. But a real one.
"...?!"
Zalario turned immediately. For the first time, genuine surprise showed in his eyes.
Behind him stood a figure.
Short, reddish-brown hair, slightly bristled from the moisture and heat of battle, framing a firm face with a strong jaw and piercing amber eyes, as alive as they were resolute.
He wore a short kimono-style overcoat, white on the outside but purple on the inside, decorated with floral petals and golden trim, floating lightly from his arrival.
His torso was bare, revealing a muscular body forged through years of combat and smithing. His right arm was exposed, marked by defined muscles; while the left was covered by a shoulder guard connected to a long red sleeve, decorated with black flame-like patterns.
Below, he wore a wide, dark brown hakama tied with a white sash. On his left leg, a side pouch was strapped on, and from his knees to his ankles, black shin guards of light armor reinforced his stance.
He wore firm, black Japanese sandals on the broken ground of the labyrinth.
In his right hand, he held the broken hilt of a katana. The blade was gone. Only scattered fragments remained, falling like iron scales onto the stone.
"Damn," he muttered with irritation, yet remained calm. "It didn't even last three seconds…"
He clicked his tongue and closed his eyes in resignation.
Senji Muramasa.
The blacksmith who wasn't supposed to be there. But was.
As if fate—or rather Ramiris—had dropped him right where he was needed.
"Muramasa!" Treyni gasped.
Charys, still on her knees, smiled in disbelief.
"Took you long enough. I thought you'd become a temple decorator."
"Not my fault," he replied without turning. "Ramiris dropped me here without a word. I figured it'd be fun to stay."
Zalario, analyzing the situation with hawk-like eyes, muttered:
"…A physical slash technique… projected with attribute-less magic…"
An evaluative glint passed over his face.
"You're not an ordinary man."
"And you don't bleed that easily," Senji replied coldly.
Treyni slowly stood up, ignoring the pain in her torso through sheer will.
Charys did the same, using her remaining arm for support.
"An opportunity like this… can't be wasted."
"Three against one. Even if it's Zalario… we might make him lose more than time."
Senji Muramasa made a hand gesture.
And then, the impossible happened: another katana appeared, forged in the air like a thought turned to steel.
Red like the sunset. Alive like hatred. Cold like duty.
"I don't care if they break," he said, raising the weapon. "As long as they can cut."
The three of them charged forward.
And at that instant, time resumed... for them.
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Flashback.
The air trembled softly, not from heat or wind.
But from something that shouldn't exist: a rift in reality itself.
A diagonal slash carved the sky above the forest clearing, glowing like an open wound in the fabric of the world. The edges hovered for seconds, and fragments of "sky"—crystalline shards from a broken dimension—fell like scales.
Then, slowly, as if the universe mended itself, the rift vanished. As if it had never been there.
A few meters away, Senji Muramasa sheathed his katana in a slow motion, as if what he had just done didn't deserve urgency.
His reddish-brown hair shifted lightly with the breeze. His bare torso was covered in sweat. The red shoulder guard on his left arm crinkled with every movement.
"…Tsk. He did it again," muttered a deep, contained voice.
Kurobe, the Oni blacksmith, watched from a nearby rock, arms crossed, his face caught between awe and resignation.
"You can't keep pretending that's normal, Muramasa. You just cut reality itself. Do you know what that means?"
Senji tilted his head.
"…I cut reality?"
"Pieces of the sky fell! That's not a metaphor!" Kurobe protested, pointing to the ground where tiny glowing fragments still sparkled. "How did you do it?"
Silence stretched for a few seconds.
For the first time, Senji looked uncertain.
"I didn't think much about it."
"What?"
"I just… felt the blade needed to go further. Like something invisible was waiting to be divided. The cut wasn't physical… it was more like… belief."
Kurobe raised an eyebrow.
"Belief?"
"Haven't you read old myths? Or stories from a time when people did impossible things?"
"I thought those were drunk tales…"
"So did I."
Senji looked up at the now-whole sky.
And without hesitation, swung again.
Space split.
Ethereal fragments fell again.
And the void tore like crumpled paper.
Kurobe was speechless. He just exhaled.
"…What kind of freak are you…"
Senji barely smiled.
Then the two of them sat beside the clearing, without hurry.
They spoke of techniques, metals, impossible combinations.
Kurobe joked that maybe a spatial distortion field could be countered if you altered a sword's point of contact with space before it warped.
Senji didn't answer.
But the phrase stuck in his mind like an incision:
"Spatial distortion…"
"Could someone actually manage something like that?"
Minutes passed in silence.
Senji finally stood, brushing dust off his brown hakama.
"I'm going to travel a bit."
Kurobe tilted his head in confusion.
"Now? Where to?"
"Not sure exactly. But I think someone's waiting for me somewhere."
Kurobe sighed.
"At least tell Rimuru and Ciel, alright?"
"You tell them. You're better with politics."
Senji raised his hand in farewell.
And with that, he walked into the forest, vanishing behind a ripple in space, as if reality gently absorbed him.
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Weeks had passed since he had left Tempest without directly saying goodbye to Rimuru and Ciel.
Senji had wandered through underground markets, nomadic blacksmith villages, elven lands where swords were crafted with wind and crystal, and dwarven fortresses where hammers beat rhythms older than language.
In every place, he observed. Sometimes he worked under another name. Other times, he simply listened and ate in silence.
No one asked too many questions. And those who did never fully understood what he was looking for.
He didn't want a sword that was merely "strong."
He wanted a sword that could break what shouldn't be broken.
One that would defy the logic of space and treat it like just another obstacle.
Days later, atop a mountain forgotten by maps, Senji stood alone before a makeshift anvil.
Around him, there was nothing but black stone, mineral veins, and the silence that only places untouched by humans can offer.
His clothes were covered in dust. His white-and-purple overcoat hung from a nearby rock.
His bare torso shimmered with sweat under the dim sun. The red shoulder guard on his left arm vibrated faintly with every strike.
Clang.
Clang.
Clang.
Each hammer strike had purpose. Each tension line in the metal responded to the echo of his thoughts.
"Spatial distortion…"
"It's not about cutting what you see… but cutting what shouldn't exist."
Sharpness wasn't enough. Speed wasn't enough.
He needed a projection structure that would insert itself into space before it could warp.
A sword that didn't clash with the distortion—but treated it as false space to be corrected.
Hours later, with rocks steaming around him and his breathing steady, Senji lifted the material.
It was raw, rugged. But not ordinary.
A dark block that didn't reflect light or emit heat. It seemed to absorb existence itself.
An astral core, brought from the skies by an unnamed merchant. They said it had formed in a magical storm centuries ago.
Senji didn't believe the story. But the metal… responded.
It spoke to him.
He went two days without sleep.
The magical projection inside him vibrated on the edge of collapse.
Ciel's energy, still latent in the crystals within his side pouch, stabilized the patterns the metal tried to reject.
Clang.
Clang.
Craaaack.
A slight crack on the surface revealed the internal cut of distortion. The forge, for an instant, reflected a space that wasn't real.
Senji didn't blink.
"Almost…" he whispered.
"Just a little more."
He hammered on.
Not for a perfect sword.
But one that could be projected, reproduced, and destroyed—always with the same goal: to break the lie of altered space.
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The anvil still smoked.
The last traces of magic dissipated into the rocky air while the sky turned a deep reddish hue, stained by the sun setting behind heavy clouds.
Senji Muramasa, covered in ash, looked over the still-tempered metal.
His breathing was calm, but his amber eyes shone with something more intense: purpose.
That's when a shadow emerged behind him without warning.
An unnatural silence preceded its arrival. A rift without pressure, a presence without weight.
"It's unusual to find you in such a remote place, Senji Muramasa."
The voice was soft, melodic… but dangerously composed.
Senji didn't turn.
"And it's rare for you to use my full name, Diablo."
The demon appeared beside him, without transition. As if he had always been there.
He wore black—elegant, immaculate—even among volcanic dust and broken stone. His golden eyes, with red pupils and black sclera, observed him with surgical precision.
"It's been weeks. I thought it prudent to ask whether you planned to return… or if you intended to make my dear Rimuru-sama suffer forever."
Senji clicked his tongue and set the hammer aside.
"I don't intend to make her suffer. I just… needed a little more time."
"For what? Isn't your search over?"
Senji didn't respond right away.
He lifted a small transparent vial where pale blue particles floated, like suspended flakes in water.
Crystals infused with Ciel's energy.
"I'm close. Very close. I just need to understand one last thing…"
Diablo raised an eyebrow, almost intrigued.
"And that last thing is…?"
Senji murmured, as if speaking to himself:
"…how to pierce not space, but the intention behind its distortion."
Diablo narrowed his eyes.
"You've always had a peculiar way of seeing things. Do you really think your sword can reach an intention? That's not cutting… that's rewriting."
Senji finally looked at him—without arrogance, without submission.
"What I forge isn't a weapon, Diablo. It's an answer."
The demon surveyed the surroundings, the anvil, the cut marks in the rocks, and the dense air filled with magical residue.
"I'll give you a few more days."
Senji raised an eyebrow.
"You'll give me?"
Diablo smiled—humorlessly.
"No. She gives them to you. I am merely her will made word."
Senji took a deep breath. The heat of the mineral still pulsed on his skin.
"Just a little longer… just a little more."
Diablo vanished like smoke before replying.
But a phrase lingered in the air, as if he had left it behind on purpose:
"Don't take too long, Muramasa. If you're the one who made Rimuru-sama cry... I will kill you."
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The empty corridor of the labyrinth echoed with hollow sounds.
The stone walls weren't real at that level of depth. The dimension twisted, vibrated, as if space itself refused to be tangible.
Senji Muramasa walked in silence.
His cloak was folded and tied to the pouch on his left leg. His bare torso bore fresh scars from magical friction.
His amber eyes, dimmed by doubt, stared at the uneven ceiling.
What unsettled him weren't the wounds, nor the battle ahead.
It was Diablo's voice still echoing in his mind.
"I'll help you."
Senji came to a sudden stop.
"…Why?"
The question was answered long after it was asked, in the in-between plane where Diablo emerged from the shadow as if he had always been there.
"Because it would benefit me to tell Rimuru-sama… that I was the reason you didn't die."
A dry, raw silence.
Senji lowered his gaze… and chuckled quietly.
"…I guess I'm not surprised."
He rubbed the back of his neck, uncomfortable.
"But thanks, anyway."
Diablo smiled with his usual cold calm, then vanished once more.
"Don't waste my support."
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Senji Muramasa's body was sent flying backward, rolling across the cracked ground.
His shoulder dislocated from the impact.
Treyni screamed his name. Charys barely managed to intercept another of Zalario's blasts with her remaining arm.
Zalario walked calmly among them, like a theologian stepping through the ruins of a broken chapel.
"…You are persistent."
Senji spat blood. He tried to get up. Failed.
But his fingers moved.
And a katana materialized in his palm.
Zalario raised an eyebrow.
"You can still…?"
At that instant, something changed.
Senji's eyes began to glow…
They were no longer amber.
They turned golden, like liquid flames.
The pupils narrowed into vertical red slits, like a seal.
The black sclera consumed the whites of his eyes.
For a moment, it seemed reality trembled just from looking at him.
Zalario took a step back. His instincts—honed through eras of mystical strategy—whispered without words:
"He… is not alone."
Senji's aura changed.
It was no longer just his.
It was as if another consciousness shared his magical flow. Not a possession. But perfect synchrony—like two artisans forging from the same core.
And within that core… was something ancient, demonic, structured… and infinite.
"He's being supported…"
"By who?"
The katana in Senji's hand glowed crimsona—then black.
A blade that cut not with technique… but with borrowed intention.
Zalario smiled faintly.
"…So this is all you've got. Very well. Show me that foreign will."
Senji rose to his feet.
A new katana was born.
And the battle continued.
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Final Note:
Hi there!
It's been a while!
Truth is… I went on a sabbatical and didn't continue the story, hahaha! But setting that aside…
Let's talk about something important.
As you probably read in this recent chapter, we've officially crossed into the Tensei Shitara Slime Datta Ken canon. Yes! No more floating in romance. Now, Senji Muramasa is right in the middle of Volume 16, fighting alongside Treyni and Charys against none other than Zalario.
And all of that… with his own projected swords, and a little infernal help from Diablo.
Now I want to hear from you:
Did you like how the integration was handled?
Did it feel like Senji fit well into the canon?
Do you have different ideas about how you would've done it? I'll be reading your opinions—whether you agree with this chapter or want to share how you would've liked Senji to enter the canon.
Thanks for sticking around, for your patience… and for your support!
I promise not to take another sabbatical this long (maybe!).