Multi Dimension Shop

The moon rose over Fuyuki City, casting silver ribbons of light across deserted streets. High in the sky, faint wisps of cloud drifted like silent omens. Somewhere in the shadowy alleys beneath, a girl in crimson and black sprinted with a singular focus: Rin Tohsaka. Her newly acquired ring—the Starweave Ring purchased from Takashi's interdimensional Shop—glimmered on her finger. Tonight, it would face its first true test.

The Mage's Battlefield

Leaping atop a stone wall, Rin paused to survey the courtyard of an abandoned churchyard. The Holy Grail War had begun in earnest, and the city was strewn with potential battle sites. Tonight, she had intercepted word that one of her rival Masters planned to make a move here.

She knelt, palm against the weathered stone, focusing on the pulses of mana in the air. The Starweave Ring pulsed gently against her skin. With each breath, she felt her mana flow more naturally, more efficiently—like a smooth current of water instead of a choppy stream. Even her concentration felt clearer, as if the ring blocked out the uneasy dread that often accompanied Grail War showdowns.

"So it does work," she thought, recalling the day she had discovered that unassuming door in the Tohsaka mansion's cellar. Or, more accurately, the door had manifested itself to her the moment her curiosity peaked in her scrying ritual. Through that door, she had met the mysterious Takashi—who claimed to run a shop connecting countless worlds. She had initially been suspicious, but curiosity and desperation made her strike a bargain. The Starweave Ring was hers now, in exchange for a portion of Tohsaka gemcraft knowledge offered as trade.

Rin still felt the sting of giving up some of her family's secrets. Yet, at this moment, the ring's tangible power more than justified her sacrifice. "At least Takashi promised not to sell that knowledge to anyone from my world," she consoled herself. "Small comfort, but comfort nonetheless."

A rustle of wind behind the church. Her head snapped up. They're here.

She leapt down with practiced grace, landing in a swirl of red skirt and black stockings. Her polished boots crunched on the gravel path. Dim moonlight illuminated the yard's swirling old tombstones. And in that half-light, a male figure in a dark coat came into view, posture rigid as he turned.

Rin recognized him: Kayneth Ashfield El-Melloi, an esteemed magus from the Clock Tower. But something was off: though Kayneth had once participated in a prior Grail War, he shouldn't exist in this particular timeline of events, at least not in the capacity of an active Master. Yet the complexities of the Grail War—parallel timelines, irregularities—sometimes allowed for unorthodox participants to slip in. He might have discovered an artifact that bridged realms or used a leftover command spell. Regardless, he was here, and his presence spelled danger.

"Rin Tohsaka," Kayneth greeted, voice echoing across the courtyard. "Your family's magecraft precedes you. I had hoped we would not need to cross paths."

Rin's eyes narrowed. "And yet, you're here, in the middle of the night, rummaging around a place tied to the Church's secrets. Seems to me you're looking for trouble."

With a flourish of his hand, Kayneth summoned a swirling sphere of silvery liquid—a familiar presence known as Volumen Hydrargyrum, the mercury-based mystic code capable of both offense and defense. "Your father was once an associate of the Mage's Association," Kayneth said, stepping forward. "But this is the Grail War. Alliances matter little if they stand in my way. And the Tohsaka name is hardly one to be trifled with."

Rin felt her heart pound. In the previous timeline, Kayneth was formidable—adept in controlling that mercury sphere for illusions, traps, and lethal strikes. She needed an advantage.

The Starweave Ring warmed on her finger, as if responding to her tension. "So be it," she thought. "Let's see if this ring is worth the price I paid."

Testing the Ring

Kayneth wasted no time unleashing Volumen Hydrargyrum; the mercury formed a whip-like tendril, lashing out in a swift arc. Rin jumped back, brandishing a small collection of gem talismans. In her old routine, she'd typically have to carefully gauge how much mana she could channel into each gem. Overloading them risked backlash. But now, with the ring, she sensed a smoother flow, less friction, and a calmer mind.

Her first gem glowed a bright cobalt as she murmured an incantation under her breath: "Fracture and Bind!" A crackling lightning chain erupted from the gem, wrapping partway around the mercury whip. Blue sparks sizzled on contact with the silver surface, forcing Kayneth to momentarily retract the fluid mass.

But Kayneth was no novice. He sent another portion of the mercury oozing across the ground. Rin, eyes sharpened, felt the ring's influence guiding her focus. "He's trying to flank me," she realized, pivoting on a heel to release a second gem's stored fire spell. Flames erupted in a tight spiral, scorching the creeping silver and halting its progress.

In the back of her mind, a flicker of amazement formed. "It's never been this easy to cast in quick succession." Usually, gem-based spells drained her mana in bursts, forcing her to maintain composure between castings. Tonight, however, her reserves felt better regulated. The ring's 30% efficiency boost wasn't just a statistic—it was a tangible difference that let her chain spells with minimal downtime.

Emboldened, she advanced, using the element of surprise. "You're not the only master of advanced magecraft," she declared.

Kayneth's eyes narrowed. He formed a spherical barrier of mercury around himself, repelling the high-temperature flames. "I see you're well-prepared," he said, voice echoing from within the shimmering orb. "But your trifling illusions of improvement won't last. Volumen Hydrargyrum is unstoppable."

"Careful with that confidence," Rin shot back, snapping her fingers as she flung a gem underhand. A radiant glyph flared at her feet, channeling energy upward. "Starlight Lattice!" She invoked a high-level binding spell newly adapted from her gemcraft knowledge. The ring's mental interference protection kept her focus unbroken despite Kayneth's attempts at subtle illusions.

Threads of sparkling mana wove around Kayneth's barrier, latching onto the mercury's swirling shape and anchoring it to the ground. He visibly struggled to break free, lines of tension across his face. "What is this…?"

"Don't assume you're the only one with advanced mystic codes," Rin retorted, referencing the star-laced ring that glinted on her finger. She poured additional energy into the binding. In a normal scenario, this kind of high-level layering would leave her short of breath—but the synergy with the ring kept her stabilized.

Kayneth's barrier quaked, cracks forming in the mercury. Realizing the threat, he retracted part of the fluid into a narrow spear that lunged from a gap. Rin dodged, nearly losing her concentration. But the ring's protective wards against mental interference eased the mental strain. She managed to maintain the binding circle's cohesion, forcing Kayneth further into retreat.

With a triumphant gleam in her eyes, Rin prepared a finishing blow—channeling a powerful elemental attack into a final gem. A swirling sphere of condensed wind shimmered in her hand. As Kayneth's mercury barrier wavered, she flung the sphere forward, the gem exploding in a violent gust that rocked the entire yard.

Boom!

Gravestones cracked. Dust billowed in a cloud. When it cleared, Kayneth's barrier lay in fragments, half the mercury forced back into its container. Kayneth himself had been thrown against a broken statue, trembling as he tried to stand.

"You… wretched brat," he spat, struggling for composure. "No typical Tohsaka mage should be able to handle these spells so fluidly."

Rin's cheeks were flushed, adrenaline coursing. Even with the ring, it had been a tough match. But she had the upper hand. She stepped closer, emerald eyes flashing with resolve. "You're outclassed. Leave this war, or I'll ensure you can't crawl back next time."

Kayneth grimaced, but fear flickered in his gaze. Though pride weighed on him, he understood she had cornered him. Slowly, the battered magus released a shuddering breath. "Very well," he said, voice brittle with resentment. "But this isn't the end. The Grail War is far from decided."

With a final glare, he slunk off, the battered remains of Volumen Hydrargyrum swirling around him like a wounded serpent. Rin stood in the courtyard until she was certain he was gone. The air felt heavy, filled with the echoes of clashing spells.

Finally, she exhaled, letting her shoulders drop. Tension drained away, replaced by a wave of relief. She looked down at her ring. The faint glow had subsided but remained warm against her skin. "You lived up to your promise," she said softly, remembering Takashi's earnest explanation: "It won't make you a demigod, but it'll refine your mana usage and ward your mind from meddling."

She brushed dust from her skirt, allowing a brief smirk. "This advantage might be what I need to claim the Grail." Yet, the reminder of that cosmic door tugged at her thoughts. Should I return to that shop? She was cautious, but she couldn't deny the appeal of more items to bolster her chances.

"Not tonight," she decided with a quiet sigh, glancing at the bruises forming on her arms. "But soon."

Meanwhile, in Takashi's World

A soft chime rang through the Shop. Takashi, hunched over the counter, blinked awake from a light doze. He glanced at the dimension door in the back—it remained shut. Yet the System interface popped up in front of him, swirling with subtle patterns.

System Notification: "Item purchased by Customer #1 has been used in combat. Usage successful. No issues detected."

Takashi's lips curled into an amused smile. "Customer #1. That's Rin. I guess she tested the ring." The notion that the System was monitoring item usage to some extent was equal parts reassuring and unsettling. He wondered what sort of battle she'd faced—if she'd come out unscathed. There was a subtle satisfaction in knowing he'd helped a legendary magus—someone he'd admired in his prior life—gain a small edge.

He closed the interface, letting his eyes drift across the Shop. Shelves of bizarre potions, boxes of weird trinkets from myriad worlds, carefully locked cabinets containing mystical blades and advanced firearms. The swirl of possibility hovered in the air, and it always amazed him that so few people knew of this realm.

He was about to get up and make himself a cup of coffee when a stirring near the door caught his attention. The dimension door's edges glowed faintly, lines of runic script shimmering along the wood. A new visitor? Or perhaps… Rin again?

Takashi's heart rate quickened. Even though he was "invincible" inside this building, each arrival carried an unknown. He straightened his collar, stepping toward the door.

Creak.

The handle turned. A faint gust of wind rushed in, carrying the fragrance of night-blooming flowers. Then, stepping through that crackling veil of cosmic light, came a figure he didn't recognize at all.

She was petite, her hair in two braided loops on each side of her head, dressed in what appeared to be an old-fashioned Chinese qipao in pale pink. Her eyes sparkled with curiosity as she glanced around, her expression a mix of awe and confusion.

Takashi frowned for a moment, racking his memory. She didn't match any character he immediately recognized from the more famous anime series. Then again, the Shop spanned infinite universes, some more obscure than others.

"Um… excuse me?" she said softly, stepping onto the wooden floor. "I'm not sure how I… got here." She peered over her shoulder at the still-glowing portal.

Takashi offered his warmest customer-service smile. "Welcome to my Shop," he said, repeating his practiced line. "A place that bridges different worlds. My name's Takashi."

The young woman's eyes widened. "B-bridges… worlds?" She turned in a circle, marveling at the bizarre mixture of shelves—chips, candy, potions, swords. "This is so strange." Her expression lit with shy wonder. "I was trying to brew a special medicinal soup for my grandmother's illness, and I prayed for a miracle. Then… I saw a door appear behind my stove. And now I'm… here."

Takashi exhaled, relieved that she didn't appear hostile. "Well, you've come to the right place if you need something extraordinary. We stock medicines and potions as well. The only question is what you're willing to trade or pay."

She bit her lip. "I… I don't have money. At least, not much. My family is struggling." Then she glanced down at a small woven pouch at her waist. "But I do have some prized herbs from the mountains near my village. They're said to have magical properties. Maybe it's worth something?"

Takashi beckoned her toward the counter. "We can check the System and see what we can do. No harm in asking."

The girl carefully placed three dried, twisted roots onto the countertop. They gave off a faint glow, almost like living embers. "They're called Moonlight Ginseng. Very rare," she said earnestly. "They're said to heal internal wounds, but by themselves, they're… not powerful enough to cure my grandmother's disease."

Takashi nodded, softly activating the scanning interface. A swirl of blue light enveloped the herbs, while the System ran its valuation. Moonlight Ginseng: extremely potent natural healing catalyst. Shop Credit Value: 700 per root.

He turned back to the girl, managing a reassuring smile. "The Shop says each root is worth about 700 credits, meaning your total is 2,100. That's not bad." She blinked, uncertain of what "700 credits" truly meant, but she seemed heartened it wasn't worthless.

Takashi opened the item catalog, filtering for "Health & Recovery." Rows upon rows of potions, pills, enchanted foods, and medical devices scrolled before his eyes. He whistled. "We have quite a range. Let's see if there's a remedy that suits your grandmother's ailment."

After some brief searching, one potion caught his attention: "Arcus Vitae Elixir: Fully cures most ailments stemming from corrupted mana or spiritual infection. Mild to moderate effect on purely physical diseases, but can accelerate healing." Cost: 1,200 Credits. Another item, "Evergreen Leaf Tonic," priced at 2,000 Credits, was a potent healing agent for advanced diseases, but with a slower, gentler approach.

He explained both options to the girl, who listened with rapt attention. "If you want to be certain, the Evergreen Leaf Tonic is probably your best bet, though it costs 2,000. You have enough credit to cover it with your herbs. That would leave you 100 leftover."

Her eyes shimmered with tears of gratitude. "That's… that's wonderful. I'll take the Tonic."

Takashi initiated the trade. The System's subtle glow enveloped the dried roots, whisking them away to the unseen stock vault. In return, a delicate bottle appeared on the counter, filled with a brilliant green liquid that sparkled faintly. The girl's hands trembled as she picked it up.

"Thank you," she whispered, voice choked with relief. "Thank you so much. I'll… I'll go give this to my grandmother right away."

He gave her a small bow, stepping around the counter to guide her gently back to the dimension door. "Just remember, there's nothing free—everything has a price. But I'm glad we could help. The door will take you back to where you came from."

She turned, about to step through. But she paused, a small frown creasing her brow. "Could I… come back?" she asked quietly, meeting Takashi's eyes. "If I need to?"

He nodded. "Yes. The door appears when you truly need it—and have something to offer. It'll open again if your desire is strong enough."

She held the Tonic close to her chest. "All right. Thank you… Takashi." And with that, she disappeared through the portal, the door shutting with a soft click behind her.

A Return and a Conversation

The Shop was quiet once again, leaving Takashi to reflect. Each new customer brought their own story, each transaction shaping the fates of worlds. He found himself empathizing with the girl's desperation. Not every visitor was a mighty warrior or cunning mage. Some were ordinary people who simply needed help that their own world couldn't provide.

He turned off the scanning interface, heading back to the front to rearrange some stock. But as he passed the dimension door, it glowed once more. A third time tonight? That was unusual.

His heart jumped. Could it be Sasuke again? Or another new face? He braced himself.

The door swung open—and Rin Tohsaka stepped through, still in her characteristic red top and black skirt. The moment she crossed the threshold, she practically sagged against the doorframe, breathing heavily. Sweat clung to her brow, strands of dark hair plastered to her cheeks. It was clear she had recently been in a heated confrontation.

Takashi hurried over, worry etched on his features. "Rin? Are you all right?"

She scowled, waving off his concern. "I'm fine," she snapped. But the tension in her voice betrayed exhaustion. After a moment, her posture relaxed a fraction. "…I just came from a rather intense battle. I used the ring." She lifted her hand to show the Starweave Ring glinting on her finger. "It worked, but… wow do I feel drained now that I'm not fighting."

Takashi offered a steadying hand, guiding her toward a small wooden stool near the counter. "Sit," he instructed gently. He rummaged under the counter, producing a bottle of water. "Here, it's just regular water, but it helps."

Rin hesitated, then accepted the bottle, taking a couple of long sips. The cool liquid soothed her throat. "I had to fend off a powerful magus," she said, catching her breath. "But the ring gave me enough advantage to drive him away."

Takashi nodded, quietly relieved that she'd come out on top. "I'm glad it served you well. No issues with mental interference or illusions?"

She shook her head. "No, it actually helped me keep my focus. Usually, after stringing together multiple gem-based attacks, I'd be dangerously low on mana. But I had enough synergy left to land a finishing blow." She paused, eyeing him levelly. "…Thank you."

He blinked. It wasn't often one heard genuine gratitude from Rin Tohsaka. He offered a soft smile. "You're welcome. And for what it's worth, I'm happy it worked."

A moment of silence passed, Rin fiddling with the ring on her finger. Then she looked around the store, taking in the bizarre mix of everyday goods and arcane items. "I… wanted to see if you had anything else that might complement this ring. I don't need more raw power right now, but something to handle prolonged battles or complicated magical effects." She frowned slightly, remembering Kayneth's fluid illusions. "Maybe a countermeasure for magical entrapment or domain control."

Takashi considered. "We do have a variety of wards. Let me check…" He invoked the System display, scrolling through "defensive accessories." Her eyes flicked to the scrolling holograms, now somewhat accustomed to the phenomenon.

At length, Takashi paused on an entry: "Everglow Ward Pendant"—a small crystal on a silver chain that passively expands the wearer's field of stable mana, reducing the effect of localized illusions or domain-based distortions. Perfect for preventing forced teleportation or illusions that rely on environmental manipulation. Cost: 3,000 Shop Credits.

Rin leaned closer. "That's… interesting. It would have made that mercury labyrinth much less effective." She tapped a finger on her chin. "But do I even have enough currency or trade value left?"

Takashi glanced at her. "The ring cost you some Tohsaka gemcraft knowledge, but you still have enough for a partial exchange if you have more valuable techniques or items. Or if you've collected mana crystals, relics, anything. Another approach is to pay in your world's currency—though the conversion rate might be steep."

Rin pursed her lips. She had some more advanced gemcraft formulas, but not something she was eager to part with again. However… there was a lesser technique she'd researched that involved layering timed gems for delayed spells. It wasn't a direct Tohsaka secret—more of an offshoot she'd developed. Perhaps that would suffice.

She proposed the trade, carefully describing the technique while the System scanned her words, analyzing them as intangible data. The floating runic script glowed softly: "Trade Value: 2,500 Shop Credits."

"That's short by 500," Rin murmured, disappointment creeping in. She rummaged in her pockets, producing a single high-grade mana crystal. The System recognized it: 300 credits. Still 200 short.

Takashi frowned, thinking fast. He knew better than to push her into trading away family secrets. "System, can we do partial currency conversion on top of these items?" he asked out loud.

A gentle swirl of light. "Affirmative. Currency from Dimension 'Fate/Nasuverse' can be converted. User must provide 200,000 yen equivalency."

Rin looked at him skeptically. "200,000 yen? That's not a small sum." She sighed. "Still, it might be worth it if the pendant is as good as it sounds."

Takashi, wanting to sweeten the deal, gestured to the Shop's smaller, everyday goods. "We're not strictly stuck on cash. If you have something else—like a mystic code you don't use or a minor relic—maybe that can cover the last 200 credits?"

Rin mulled it over and finally pulled out a small crystal rod from inside her jacket. "This is a tracer gem I used for familiars," she explained. "I have better versions now, so it's not as valuable to me." The System scanned it. "Trade Value: 250 Shop Credits." Enough to cover the difference.

A flash of light enveloped the rod, the mana crystal, and the intangible knowledge data. In exchange, the silver chain and crystal pendant materialized in Rin's hand, glowing with faint teal luminescence.

She exhaled in a rush, eyes drinking in the subtle glow. "Everglow Ward Pendant… Let's hope it lives up to its name." A small smile touched her lips as she put it on. Immediately, she felt a gentle, stabilizing presence that spread around her like an unseen bubble.

"Good," she murmured, giving Takashi an acknowledging nod. "This will definitely be useful."

Takashi felt a wave of satisfaction—another successful transaction. He was about to ask if she needed anything else when she suddenly turned thoughtful.

"You know," Rin said quietly, "I used to think only the Holy Grail War determined who rose or fell in mage society. But now, with your shop…" She trailed off, scanning the shelves lined with an impossible inventory. "One item can tilt the balance in someone's favor, disrupt entire storylines. You've essentially become a hidden factor in countless worlds."

He folded his arms, eyes lowering. "I've thought about that too. But the Shop states the buyer's will is what determines how the items are used. I just… facilitate the trade." He paused, glancing at her. "Still, I won't lie—sometimes I wonder if I'm messing with destinies."

Rin let out a rueful laugh. "Destiny is shaped by choices, not inevitabilities. If someone finds your door, it means they had a strong desire—and the means to pay. It's not as if you're forcing anything. You're just… an option, a cosmic merchant."

He gave a small nod. "Thanks. That's how I try to see it." Then he offered her a brief, playful smile. "Though you're one of the few who actually came back. I guess that means I did something right."

She smirked, crossing her arms. "Don't get cocky, shopkeeper. I came back because your merchandise is top-tier, not because of your charm."

Takashi chuckled. That was more like the Rin he knew from the stories—sharp-tongued but not unkind. "Fair enough. Are you heading back to your war tonight, or do you want to rest here a bit?"

She considered the idea of resting, but quickly shook her head. "It's not safe to linger too long; the War moves fast. And I'm not sure how time flows differently between our worlds." She pushed off the stool, giving him a final, measured look. "But I'll probably be back, eventually. Depends on how things progress."

"Just remember you're always welcome," Takashi replied. "And you know the rules—nothing's free, everything has a price. But I'll do my best to be fair."

She nodded. "Right. Well then… see you around, Takashi." With those words, she turned and crossed the threshold back to her world, the swirling door sealing in her wake.

The store fell silent again, leaving Takashi to reflect on the strange mixture of relief and satisfaction that came from dealing with repeat customers. Rin had used the ring successfully—and wanted more. Maybe that meant the "System Shop" was truly carving a niche in these worlds, becoming an indispensable resource.

Takashi glanced at the ledger that the System maintained. His current Shop Credit balance glowed softly in the air:

Previous Balance: 2,600 Credits Trade Gains (Rin's new deal): +3,000 Credits Net Transaction Costs (pendant restock): –2,400 Credits (the System's internal cost for obtaining the item from the infinite inventory) Resulting Balance: 3,200 Credits

He exhaled with a small sense of triumph. The Shop was profitable—and that meant inching ever closer to the day he could purchase the Shopkeeper's Gate ring for himself, ensuring he could teleport back to safety if threatened outside. Another 1,800 or so Credits, and he'd be there.

A swirl of possibility, he mused. Day by day, transaction by transaction, countless stories converged here. Rin Tohsaka, Sasuke Uchiha, that kindhearted herbalist girl… who's next? The dimension door flickered gently in the dimness, as though echoing his question.

He stepped up to the door, placed a palm against it, and felt the hum of the cosmic gateway. "We have everything, but are they willing to pay the price?" he whispered, repeating the old refrain.

Something about that statement made him pause, a ripple of unease in his stomach. The words were meant for customers, but at times it felt like the Shop was also reminding him. For all the wonders he sold, the price on his end was an ever-growing awareness of how precariously entire worlds hung in the balance of these trades.

In that silence, he recalled Rin's perspective: Destinies are shaped by choices. He let out a breath, feeling oddly heartened. "Then I'll make the best choices I can," he said quietly. "I won't cheat or exploit them. The rest is up to them."

Satisfied with that, he finally locked the front door to the Tokyo street. Another day in the life of an interdimensional merchant was coming to a close. Or perhaps, just beginning—time itself seemed to warp here, day melding with night whenever the dimension door decided to open.

Takashi snatched a can of coffee from one of his own shelves—"Be your own best customer," he joked to himself—then settled down behind the counter, glancing one last time at the portal. The ring that Rin had used was just one among thousands of possible items. For better or worse, each trade would cast ripples across an entire reality.

Even so, at least for tonight, the door seemed content to remain still. And for the moment, that meant Takashi could savor a few minutes of peace, sipping from his coffee can, imagining the countless stories unfolding in the realms beyond.