Note:
I ended up liking the story of Senji Muramasa x Alaya, so I decided to write this story of Senji Muramasa x Rimuru Tempest instead. I've always liked Rimuru, so let's go for a story with this pairing. I hope no one gets upset. Also, I must mention I have no real knowledge of Tensei Shitara Slime Datta Ken. I only watched the first season, and that's about it—I didn't continue with the anime/light novel/manga. But as I said, I like Rimuru a bit, so in this story, Rimuru Tempest will be female. I hope no one minds that—it's just a fanfic, a slice-of-life story set in Senji Muramasa's forge, where little by little, his relationship with Rimuru Tempest will take shape.
Also, I need help with Ciel. Give me suggestions on how to incorporate her into the story. She's not in the prologue yet, but I'm sure there are people who'd like to see her involved—so I'll need help with that.
Prologue
The sky above him was a vast, endless blue—immense and unknown. Senji Muramasa frowned as his eyes scanned the landscape around him. He was in the middle of a dense, vibrant forest, where the sounds of wildlife blended with the whisper of wind rustling through the treetops. It was a strange place, unfamiliar, and no matter how hard he tried to recall how he'd gotten there, his mind offered no clear answers.
He had been in his forge, as always, crafting a blade for a client he could no longer remember. Then, everything went black—and now he was here.
"What the hell is this place...?" he muttered in his rough, deep voice.
The blacksmith wasn't someone easily shaken, but even he couldn't deny how unusual the situation was. As a heroic spirit, he was used to being summoned by a Master, bound to a contract that defined his purpose in the world. But this time was different. He felt no such bond—no commands, no obligations—only an overwhelmingly abundant flow of mana permeating everything around him.
He raised his right hand to his shoulder, adjusting the white kimono draped carelessly over him. The inner lining was adorned with intricate floral patterns, contrasting with the vivid red sleeve covering his left arm, which bore flame-like designs. His exposed right arm revealed a solid, muscular build, forged through countless years at the forge. A white sash secured his black hakama pants, while shin guards protected his legs down to his ankles. Every detail of his outfit spoke of a man familiar with both discipline and function.
"Well, I can't stand around here forever," he said to himself with a resigned sigh.
The mana in the air was almost suffocating—but at the same time, comforting. It was as if the world itself were telling him he could stay, that there were no limits to his existence here. Unlike other worlds, where the scarcity of magical energy could wear down a Servant without a Master, this place was different. Here, he could survive—and perhaps even live in peace.
With one last glance at the forest, Muramasa made a decision. If he was going to remain in this world, he would need shelter. More importantly, he would need a forge.
Days passed as Muramasa devoted himself to building his home. He found a clearing in the forest, close enough to a river to ensure water supply but far from the usual paths of humans and other beings. Using improvised tools at first, he began constructing the structure that would serve both as a shelter and a workshop.
The process was arduous, but for someone like him, used to working with fire and metal, it was almost therapeutic. Each hammer strike, every plank placed, reminded him that creation was the core of his existence. The forge, above all, was his highest priority. He built the furnace with sturdy stones and materials gathered from the forest, ensuring it could withstand the high temperatures required for weapon forging.
Finally, after weeks of work, the forge was complete. At the center of the workshop, the furnace glowed with a warm radiance, the sound of the fire echoing comfortingly throughout the space. The tools he had brought with him upon his arrival were neatly arranged on a makeshift shelf.
Muramasa crossed his arms, admiring his work with a faint smile of satisfaction. "It's a good start," he said softly.
The environment began to adapt to his presence as well. Some merchants and adventurers started to pass through the area, drawn by rumors of a strange blacksmith capable of repairing any weapon or forging pieces of unmatched quality. Although he wasn't interested in gossip, Muramasa took on the jobs more to keep his hands busy than for any other reason.
What Muramasa didn't know was that his quiet refuge was strategically located between the Tempest Kingdom and a nearby human kingdom. His skills as a blacksmith would soon draw attention, and among those who would seek his services was someone who would change his life forever.
Two weeks later...
The sun was beginning to set on the horizon, dyeing the sky a warm orange that contrasted with the smoke still rising from the forge. Senji Muramasa, standing by the entrance of his workshop, watched calmly as a group of soldiers from the nearby human kingdom walked away, carrying the weapons and armor he had forged for them.
"Your work is impeccable, blacksmith! We've never seen such fine weapons in the whole region," exclaimed one of the soldiers, raising a newly sharpened sword that gleamed in the sunset light.
Another soldier, carrying a steel helmet, nodded enthusiastically. "I never thought a sword could feel so balanced. It feels like part of my arm!"
Muramasa, arms crossed, didn't show much enthusiasm at the compliments, though a flicker of pride gleamed in his golden eyes. "I did what you asked," he said in his usual tone, dry but direct. "And as agreed, I expect payment."
The group captain quickly nodded, placing a heavy leather pouch on the makeshift table beside the forge. "Here is everything we promised. Worth every coin."
Without another word, the soldiers thanked him again before leaving, their laughter and footsteps fading into the forest. Once silence returned, Muramasa sighed and picked up the pouch, checking its contents. It was more than enough to cover his needs for a while.
"Job done," he muttered to himself as he closed the forge door.
Now that night was falling, Muramasa found himself with nothing to do. All pending orders were completed, and the forge was silent for the first time in days. He decided to use the quiet moment to take care of himself.
He placed his tools in their usual spot, ensuring everything was in order, then headed inside his home. In a nearby corner, he had improvised a cold-water shower using water from the nearby river. Though not particularly comfortable, it was enough to keep him clean after a day of working between fire and metal.
He removed the kimono resting on his shoulder and untied the sash holding his black hakama. His torso, covered in scars that told stories of a past he no longer cared to remember, glistened slightly under the dim light inside his home.
The cold water hit his skin, drawing a sigh of relief from him. It was a refreshing contrast to the heat he was used to in the forge. As the water ran through his red hair and fell to the stone floor, Muramasa closed his eyes and let his mind wander.
"Another day," he thought as he finished his shower.
Clean, Muramasa dressed in a simple yukata and went to the small kitchen he had built inside his home. His stomach growled, but he had no intention of preparing anything elaborate. He opened a wooden box and took out some rice and dried fish, enough for a light meal.
He lit a small fire and began cooking, his movements methodical and efficient, as if he were forging a sword instead of making food. In no time, the aroma of roasted fish filled the room, mixing with the comforting heat of the fire.
While eating in silence, Muramasa looked out the window. The full moon lit the forest with a silver glow, and the sounds of nature were his only companions. Though his life here was peaceful, he couldn't shake the feeling that something was missing, as if this world, abundant in mana, still didn't offer him a clear purpose.
When he finished eating, he cleaned the utensils and put out the fire, ensuring everything was in its place. Finally, he headed to his room, where a simple futon awaited him. He dropped onto it with a sigh, staring at the wooden ceiling as his mind began to drift.
"I suppose tomorrow will be another day like this," he murmured before closing his eyes and letting sleep take him.
Another Day…
The sun had barely reached its peak when Senji Muramasa, now with no work at hand, was cleaning and organizing the tools in his forge. The furnace was cold, and the sound of hammer against metal had ceased for the first time in days. Although his routine was constant, today seemed to drag on slower than usual.
"Nothing to do again?" he murmured to himself, staring at the empty furnace.
Just as he considered going out to gather more materials or maybe killing time by watching the nearby river, the soft chime of a bell hanging at the entrance of the forge caught his attention. He wasn't expecting visitors.
He turned, frowning slightly, and what he saw caught him by surprise: a small figure curiously stepped into the workshop. She was a young girl, short in stature, with bright sky-blue hair falling in soft waves to her shoulders, and golden eyes that gleamed like polished gold. In one word, she could only be described as beautiful.
"Who are you?" Muramasa asked, crossing his arms as he studied her.
The girl, still brimming with enthusiasm, smiled widely. "Oh, hello! I was passing by and heard rumors about an amazing blacksmith, so I decided to come see for myself."
Muramasa raised an eyebrow, his posture firm yet relaxed. "Hm? Mind telling me your name?"
"Rimuru. Rimuru Tempest," she answered with a slight nod. "Nice to meet you."
The name meant nothing to Muramasa, but he didn't particularly care. "Well then, Rimuru Tempest, what do you want? I don't usually entertain curiosity seekers without a valid reason."
Rimuru approached the forge's furnace, examining everything with keen eyes, as though evaluating the place. "I heard you're good at forging weapons, and I want to see if that's true. I need a katana."
Muramasa blinked a few times, slightly puzzled by how confident the young girl sounded. "A katana, you say? What would someone as small as you need a katana for?"
Rimuru gave him a playful look, clearly not offended. "Oh, trust me, I know how to handle one. And I'd prefer something handmade—not those mass-produced weapons with no soul."
That comment sparked something inside Muramasa. Passion for his craft lit up in his golden eyes, if only for a moment. "Hmph. At least you know how to recognize a good blade. Fine. If you have the money, I'll take your order."
"Perfect!" Rimuru replied, her smile brightening the entire room.
Muramasa led Rimuru to the inner section of the forge, where tools and materials were neatly organized in harmony. Despite her carefree demeanor, Rimuru observed everything attentively, her golden eyes shimmering with curiosity.
"How do you want it?" Muramasa asked, pulling out a dark steel ingot that gave off a faint bluish glow, almost as if it were alive.
"Simple, but durable," Rimuru said with a confident smile. "A katana that can endure anything."
Muramasa carefully lifted the ingot, inspecting it closely. "This isn't ordinary steel," he noted. "It has magical properties—a material that can amplify its wielder's mana if forged properly. If you really know how to handle a katana, this will be more than enough."
Rimuru tilted her head with interest, impressed by the blacksmith's knowledge. "Perfect. Sounds ideal."
Muramasa nodded and began preparing the furnace, lighting the fire with quick, practiced movements. As the steel absorbed the heat, it emitted blue flashes of light, as if reacting to its surroundings. With absolute focus, the blacksmith began striking the metal with his hammer, molding it with strength and precision.
While he worked, Rimuru watched in fascination, admiring the dedication with which the blacksmith wielded each tool. The sound of the hammer on metal filled the forge, creating a constant, almost hypnotic rhythm. The atmosphere was thick with heat and the magic radiating from the steel—an awe-inspiring scene for the young girl.
Hours later, when it was finally done, Muramasa lifted the freshly forged katana, examining it with a critical eye. The blade's edge was flawless, and the blue glow from the magical steel seemed to dance like flames in the firelight. It was a masterpiece—a reflection of his skill and pride as a blacksmith.
He handed it to Rimuru, who took it in both hands, astonished by the weapon's perfection. She could feel mana flowing through the steel, connecting with her own energy.
"This is... incredible," she said, turning the katana to examine its edge. "I'll definitely keep using your services."
Muramasa scoffed, though inwardly he was pleased. "That depends on what you need."
Rimuru carefully sheathed the katana, but her mind was already brimming with ideas. "Well, besides weapons, are you good at making other things? Farming tools, kitchen utensils, that sort of thing?"
Muramasa looked at her with a mix of surprise and disbelief. "Kitchen tools? That's what you want me to make now?"
Rimuru laughed softly. "Well, you're really good with metal. Why not? And if you're good with tools, maybe you could try crafting."
Muramasa crossed his arms, sensing a small challenge in her tone. "Crafting? You mean decorative stuff?"
"Exactly. Can you do it?" Rimuru asked with a curious smile.
Muramasa let out a sigh, though a glimmer of pride lit his eyes. "I've made a hundred statues as a gift to someone before. It's nothing new to me."
Rimuru's eyes widened in surprise. "A hundred? That's impressive."
She tilted her head slightly, wearing a playful smile. "Then why don't you make a statue of me? Just to see if what you say is true."
Muramasa stared at her in silence for a moment, as if evaluating how serious she was. Finally, he nodded, arms crossed with confidence. "Fine. Consider your request accepted."
A broader smile lit up Rimuru's face. "Perfect. I can't wait to see it. I'll come back tomorrow to watch you start."
"As you wish," Muramasa replied in his usual dry tone—though the spark in his eyes revealed he accepted the challenge with a touch of motivation.
Rimuru carefully sheathed the katana and began heading for the forge's exit, turning around one last time before leaving. "So, I'll see you tomorrow, blacksmith. By the way…" she paused, tilting her head curiously, "I don't even know your name. What should I call you?"
Muramasa remained silent for a moment, as if it wasn't something he considered important. At last, he answered, directly and without hesitation: "Senji. Senji Muramasa."
"Senji Muramasa, huh?" Rimuru repeated, testing the name with a slight smile on her lips. "A good name for a great blacksmith. See you tomorrow, Muramasa."
The blacksmith gave a soft snort. "Hmph. I never disappoint."
With one last cheerful laugh, Rimuru said goodbye, her figure gradually fading into the distance. Muramasa watched her until her sky-blue hair was no longer visible, then returned to his forge.
As Rimuru walked back down the path, a small sense of familiarity took hold of her. The name Senji Muramasa… why did it sound so familiar?
A fleeting thought crossed her mind, like a quick flash—something from her past life as a Japanese girl. Something about that name echoed deep inside her, though she couldn't quite place it.
"Muramasa… is that a common surname?" she murmured to herself, slightly intrigued, but quickly brushed off the thought.
"Probably just a coincidence," she decided, shaking the feeling off as she continued on her way.
Muramasa stood still for a moment, looking over the tools in his workshop. He had accepted the request—but he knew he didn't have the right material to sculpt a statue. Though the forge was filled with supplies for making weapons, armor, and tools, a statue required a different kind of material.
"A block of marble..." he muttered to himself. "That's what I need."
The marble he used for statues was a rare type, hard to find in the surrounding area. Muramasa knew he would need to travel to the nearby human kingdom to find what he was looking for. Fortunately, he had enough money to pay for it, and with no urgent orders pending, he decided he wouldn't waste time.
With determination, Muramasa got ready to leave. He secured the forge and the house, making sure everything was in order before setting off on his small journey. He fastened a belt holding small tools and weapons—just in case—and brought a pouch with enough gold to pay for the marble.
The path to the human kingdom wasn't long, and the fresh air and rustling trees brought a sense of peace as he walked. In the distance, rooftops peeked through the trees, glowing in the last rays of sunlight.
Upon arriving in the city, Muramasa went straight to the market, where he knew he'd find a store that specialized in quality materials. It was a small place, but always stocked with the best for artisans and sculptors passing through.
The owner, an older man with a tired but attentive expression, greeted him the moment he walked in. "Ah, Muramasa! Wasn't expecting you. What brings you here today?"
"I'm looking for a block of marble," Muramasa replied bluntly. "Something suitable for a statue."
The man nodded in immediate understanding. "A special commission, huh? Let me show you what we've got."
He led Muramasa to a secluded section of the store where various marble and stone blocks were carefully stored. After examining a few options, Muramasa stopped in front of a white marble block with soft blue veining—rare, but perfect for what he had in mind.
"This one," he said finally, pointing to the block. "That's what I need."
The merchant inspected the marble and nodded approvingly. "Good choice. This one comes from the northern mountains. It's got the perfect density for fine detail work."
Muramasa pulled out a pouch filled with gold coins and paid without hesitation. "Thanks. I'll take it now."
With the marble block hoisted onto his shoulder, Muramasa retraced his steps back home. Though the trip wasn't long, the weight reminded him that while forging was his specialty, sculpture required a different kind of patience.
"This won't be hard," he thought, evaluating the block. "Even if statues are more delicate, I've made a hundred before. This'll just be a small challenge."
Upon reaching his workshop, he set the marble in a corner, making sure it was in a comfortable spot to work. Muramasa paused for a moment, admiring the block, knowing that the statue of Rimuru would not only be a work of art—but also a testament to his craftsmanship.
"I suppose I'll start tomorrow," he murmured, feeling a faint thrill for the challenge ahead. Though the work was nothing new, he enjoyed pushing himself toward perfection with every piece.
Morning light softly illuminated Muramasa's workshop, which was already prepared for the day's task. The marble block—white with soft blue veins—rested in the center of the forge, awaiting its transformation. Though Muramasa had worked on many statues before, he knew this request would demand his full attention, even if it was technically easy for him. He had sculpted hundreds of statues, and this one wouldn't take him more than a day.
"I guess it's just a matter of time," he murmured, looking at the block. "It's not as big as some I've done before, so it'll be quick."
With chisel and hammer in hand, he began to work. Every strike was precise, and the marble yielded quickly under his expert hands. Muramasa sculpted calmly and efficiently, the sound of his hammer echoing through the forge in a steady rhythm as the figure began to take shape.
It wasn't long before the forge's door opened, announcing Rimuru's arrival. She had come early, as if she couldn't wait to see Muramasa start—and maybe even finish—the statue. There was something in her eyes that showed she was both excited and curious about the result.
"Good morning, Muramasa! I'm here already!" Rimuru said with a big smile as she stepped into the workshop, full of energy.
Muramasa looked up for a moment, surprised to see her so early. "You're really that eager to see the statue?" he asked, without stopping his work.
Rimuru nodded quickly and walked closer to observe. "Of course! I was dying to see how you'd do it. It's already taking shape!"
The marble block had already become the outline of a small figure with an elegant posture—clearly Rimuru. Muramasa had progressed faster than she expected, and the statue already had a detailed expression that captured her essence.
"Is it almost done?" Rimuru asked, visibly amazed. "I can't believe you've come this far already!"
Muramasa raised the chisel and, with a subtle smirk, answered, "I've done this many times. When you know what you're doing, it doesn't take long."
Rimuru watched closely as Muramasa worked, admiring every detail he added to the statue. The figure now bore a serene expression, and the blue marble veins flowed gracefully across the surface, adding a unique touch.
"It's amazing…" Rimuru whispered, almost to herself, gazing at every feature with admiration. "You did it so fast… and it's perfect."
Muramasa, satisfied with his work, made one final touch at the edge of the statue's base. "Marble is a good material. It's easy to shape, and its hardness allows for fine detail."
When Muramasa stepped back to observe the statue in full, the marble reflected the sunlight, and Rimuru, seeing her own image carved in stone, couldn't help but smile widely.
"It's... it's incredible!" she exclaimed, staring at the statue in awe. "I didn't expect it to look this good—let alone in such little time. It's better than I imagined!"
Muramasa crossed his arms and gave a calm nod. "I'm glad you like it. For a simple commission, I finished it quickly. But it's always important to make sure it's perfect."
"It definitely is! I told you you wouldn't disappoint me," Rimuru said, still looking at the statue with satisfaction.
She stepped closer to Muramasa, smiling, and—almost naturally—gave him a light tap on the arm. "Thanks, Muramasa. I can't wait to show everyone. The statue is perfect!"
Muramasa, a little caught off guard by her enthusiasm, allowed a faint smile to cross his face. "Glad you liked it."
Rimuru, clearly pleased and full of joy, thanked him once more as she said goodbye. "I'll come back to see how it fits where I'll place it, but for now… you're a genius, Muramasa!"
With one final smile, Rimuru left the forge, leaving Muramasa alone with his finished work. As he watched her disappear down the path, a quiet sense of satisfaction settled in his chest. It wasn't just the perfection of the work that motivated him—but the simple fact that he had done a good job.
The sun shone brightly over the mansion, bathing everything in golden light as Rimuru returned home, carefully transporting the statue of herself. The white marble statue with bluish veins gleamed impressively under the daylight, reflecting the perfection of every detail masterfully carved by Muramasa.
As Rimuru approached the mansion, word of her arrival with the statue spread quickly. The citizens of Tempest, always curious about their leader's activities, gathered along the streets, eager to see the work she had commissioned.
"Rimuru-sama! Is that the statue you mentioned?!"
"It's amazing! It looks just like you!"
The townspeople stared in fascination as Rimuru reached the mansion's entrance, where a small exhibition area had been set up to display the statue. Children came up to it and touched it in awe, admiring the precision and detail with which the marble figure mirrored her appearance.
"It's perfection!" exclaimed one of the ogre soldiers, a proud smile on his face. "That artisan is a true genius!"
"It's like Rimuru-sama is standing right here!" added another, staring at the statue in amazement.
Seeing everyone's excitement, Rimuru couldn't help but blush slightly. "It's just a statue, don't exaggerate," she said—though a satisfied smile crept onto her face. People kept applauding and praising Muramasa's work, marveling not just at the likeness, but at the strange energy the statue seemed to emanate from the stone itself.
"This has to be the work of a master! Who made it?" asked one of the merchants, inspecting the plaque Rimuru had placed beside the statue.
"His name is Senji Muramasa," Rimuru replied proudly. "An exceptional blacksmith. I met him recently, but he's already impressed me. This statue is just one of his works."
The crowd began murmuring among themselves, amazed that someone so important to the kingdom like Rimuru had such a lifelike statue. The entire city began seeing the artisan with new eyes, appreciating the talent and skill he had demonstrated in such a short time.
"People must meet him!" shouted a young adventurer from the crowd. "If he makes statues like this, what else can he create? I want to see more of his work!"
"We should hold an art exhibition for him in the kingdom!" suggested another. "Who knows what else a genius like him is capable of?"
Rimuru looked around at everyone, a soft smile on her lips. To her, the statue had been a simple piece of art—but the admiration of her people made her feel genuinely proud. Not every day did such a humble commission stir up so much excitement.
'Yeah, maybe that's a good idea,' Rimuru thought as she looked at the statue with an approving gaze. 'Maybe I should invite him next time, so he can get to know Tempest and its people.'
═════•═════•
Author's Note:
This story will be told in just a few chapters, focusing on the gradual development of the relationship between Senji Muramasa and Rimuru Tempest. Their connection will grow naturally and slowly as they get to know each other better.
Since the relationship will eventually take a romantic turn, I'd like to ask: would you be interested in reading a lemon when the relationship between Senji Muramasa and Rimuru Tempest is fully established—leading to an intimate moment between the two? Any comments or suggestions are welcome. Thank you for reading!