Hours later.
The afternoon sun hung high in the sky, its light falling across grass beneath my feet. Settled in the shade of a nearby tree, Medusa held a book, adjusting her glasses at uneven intervals.
Opposite me stood Artoria with a wooden sword in hand. She held her hands near her neck, the blade parallel to her head, its tip pointed at my throat.
I gripped a similar wooden blade, letting the weapon hang at my side. My body was relaxed, stance loose, weight resting on the balls of my feet, ready to break in any direction.
"Master, you mean to say she is not the true Irisviel at all, but something akin to a blank twin of hers?" Artoria asked.
"You can think of ours as someone based on the original Irisviel."
Dashing forward, I closed the distance, sword rising in a diagonal slash tracing from her waist to shoulder.
She took a step back, calves tensing as her sword descended in an identical diagonal.
Clank.
Our weapons clashed edge to edge, the recoil pushing us both back. I flicked my wrist, chaining the deflection into a horizontal sweep at her legs.
Artoria jumped, her heels vaulting an inch above the blade's length, clearing it entirely. Mid-air, her sword swept in a horizontal arc for my neck.
I bent my spine into a backward incline, her blade's tip passing a hair's breadth from my throat. She landed a second later, and we both took two steps back, our stances the same as before.
"So, she's not Illyasviel's mother?" she asked, tilting her head.
"Irisviel is Illyasviel's mother, the original one, I mean." I nodded, and Artoria exploded forward.
Grass flattened in a straight line as her blade carved a crescent through the air, inches away from my shoulder. But a gale slammed into her chest from my thrusting sword, shoving her back, her blade skimming the corner of my coat.
I let my body fall forward at the same time, the sword's tip closing in on her chest. She adjusted her swing's angle mid-motion, the edge of her blade clashing against my sword's length.
Clang.
Both of our swords deflected wide.
"Yes, they are mother and daughter, Master," Artoria said while sliding back, her expression twisting for a fraction at the word 'daughter', gone just as quickly.
Her grip on the sword tightened, knees bending, spine compressing. "I know from the Fourth War."
She detonated.
Her body uncoiled, the wooden blade screaming in a rising thrust. I twisted my torso, her tip grazing the collar of my coat. My sword answered from below, a cut aimed at her overcommitted wrist.
She twisted her hand, shifting the wooden crossguard for a block. Splinters sprayed to our side as my blade's edge met the wood.
Then Artoria loosened her grip. Her blade fell, spun a half-circle in the air, tip toward her, pommel toward me, and her free hand snapped around the reversed hilt before it finished turning.
That pommel screamed for my abdomen.
I caught her wrist and wrenched the strike sideways. Her knee came up; my shin met it first. She answered with her shoulder, and the shove sent me skidding back.
Three steps of distance opened between us. Gone in a breath.
She came again, her sword tracing varying crescents. The first arc came high, angled for my temple. I parried it with a swipe, wood biting wood. The second chained from the first, sweeping for my ribs. I stepped inside its arc, blade grinding on blade until our swords locked, crossguards kissing.
My sword rested on her neck. Her blade on mine.
Our faces mere centimeters apart.
"Master, if I may ask," Artoria continued, her breath ghosting over my face, "what is the purpose of a blank twin? For what reason would the Einzbern create her?"
"They didn't create her. She was simply recorded in their terminal, and I pulled her out to be something akin to its weapon spirit," I clarified, shifting a fraction closer.
Our crossguards kissed. Our faces nearly did too.
Artoria flinched, grip slackening for a second before tightening harder on her sword.
"S-shall we continue, or do you require rest?" The tips of her ears were flushed red, her breathing rate climbing upward.
"One more round."
Medusa glanced up at us from her shade, kept her eyes on us for two seconds, then returned to her book.
...
..
.
The next day.
Medusa sat cross-legged on the floor of our garage, a new book in one hand. Her other arm was raised straight up, fingers spread, casually holding Mustang four feet off the ground.
I sat on the floor a short distance away, right beneath the brake system, two fingers resting on a thin steel tube stretching from a wheel deeper into Mustang's frame.
A computer sat nearby, its screen pointed toward me. Irisviel had changed the wallpaper to an image of a mechanical workshop identical to our garage. Her mini avatar moved within it, both arms wrapped around dozens of rolled-up car schematics.
"Izuru, are you about to upgrade your car's fluid brake system?" she asked, leaning closer to the screen.
"Yes. I'm about to start now that everything needed is ready," I said while glancing around, and my eyes landed on Artoria walking toward us with an empty bucket.
Reaching Mustang, she crouched and crawled under, halting beside me to push the bucket in my direction. "Here is your bucket, Master."
I nodded and pulled it over, positioning it just beneath the tube my other hand was holding.
Artoria watched my actions and shuffled closer, eyes on the tubing. "Master, what does that tube in your hand do for the car?"
Turning my face to her, I spoke, "To understand that, you first need to understand what a fluid brake system does in simple terms. Would you like to know?"
She nodded three times in succession, perhaps a little too eager, given how wide her eyes had gone the first time she saw Mustang, calling it a new 'steed.'
Further away, even Medusa's ears perked up as she glanced up from her book.
I took a slow breath and started. "Simply put: when you press a brake pedal, four tubes send hydraulic pressure to the brake pads. These pads are mounted on the edges of the revolving discs inside each wheel, making them clamp down hard."
My free hand rose, tracing a small line across the tube. A slit opened, and viscous, green, gel-like liquid seeped out, dripping into the empty bucket beneath.
"Are you following?" I shifted my gaze back to Artoria.
"Yes," she affirmed.
"When a brake pad clamps onto the revolving disc, it grinds against it to bring that plate to a stop. And since a disc is attached to the center of a wheel, the whole wheel comes to a halt."
That green fluid dripped faster into the bucket now.
"Before this, brake systems used air-filled tubes to send force from pedal to pad. Air compresses, so some of that force always got lost before it reached the pad, causing the clamp to engage nearly a second late. At high speeds, if the brake was punched hard enough, compressed air could even rupture the tube outright."
"Oh..." Artoria's mouth parted, wordless.
"So fluid systems replaced them. Liquid doesn't compress the way air does. Apply force at one end, and it arrives at the other end almost instantly, with nothing lost in between."
A final drop of green vanished into the bucket, all of its brake fluid drained out.
"However, even these fluids heat up at high speeds. Air bubbles can form inside the fluid due to boiling, and you remember what air does from earlier, right?"
"Yes. It creates resistance and increases the chance of rupturing the tube itself," she answered, her palms coming to rest on her lap.
"Therefore, we will use something more viscous, colder, and with a higher boiling point than standard brake fluid." I snapped my gloved fingers together, magic circles flaring to life on its cloth.
"And what might that be, Master?" Artoria questioned, her eyebrows raised, gaze locked onto my glove like a knight staring at a treasure trove.
Another bucket materialized beside the first. This one was filled with a glossy, silver fluid that reflected the violet glow of my magic circles across its surface.
"Processed mercury. It has a very high boiling point, remains liquid at room temperature, and transfers force faster than conventional fluids."
Irisviel pulled her gaze up from a schematic on her virtual workbench. "Izuru, isn't mercury toxic and poisonous? Are you sure you should use it as a brake fluid?"
Shaking my head, I pushed the other bucket aside to settle this new one beneath the small slit on that tube. "This is magically processed mercury prepared by Medea, it's no longer toxic or poisonous, making it precisely the best material for brakes."
Both she and Artoria nodded, but then Irisviel stepped back from her workstation. "Is there anything I can help you with?"
"I would like to contribute as well, Master," Artoria said, raising a hand.
I glanced at her, then Irisviel, then that bucket of mercury and the tube. After two seconds, I pulled aside and patted the floor beside me.
"Alright. Artoria, sit here, pull the bucket of mercury up, and hold it steady with your palm on its base."
She complied, lifting the bucket and resting her other hand flat against its base. "Now, Master?"
"Now, Irisviel, I need you to use your threads to create a thin, two-way pipe."
"Done." She said as silver threads crept out of the laptop, spinning and weaving into a pipe with two open ends with another thread connected its middle back to the laptop.
I inserted one end of that pipe into the bucket of mercury Artoria was holding, then slid the other end into that slit I had made in the brake tube.
Artoria blinked at that, her brows furrowing. "We have a connection, but how will we push the liquid upward, Master?"
Bringing my hands to rest on my knees, I pointed my chin at her. "You will be the one to do that."
"How so?"
"By using your Mana Burst at its lowest intensity possible." Her face went blank at my words.
"Come again?"
The corner of Artoria's mouth twitched before she pushed it down.
"Use your Mana Burst on the base of this bucket to propel the fluid up and into that tube."
"Master... You want me to use my Mana Burst like a mundane motor?" Her grip tightened on the bucket, a crack ringing out from its metal.
"Yes. Is there a problem with that?" I tilted my head, voice even.
She swept her gaze around our garage, and after a full sweep, her gaze landed back onto the bucket. Her free hand opened, closed into a loose fist, then opened again, finding nothing useful to do. "Master, won't all the fluid fly out of the bucket if I use Mana Burst?"
"Irisviel." More threads expanded from that pipe, stretching over the bucket to seal it like a lid.
"You can proceed without worrying now," I said after closing my eyes.
Artoria glared at me for three seconds before snapping her attention back to the bucket. Gold flared from her index finger as she tapped it against the bucket's base.
A thrust of raw force launched the mercury up through the pipe into that tube, and just before it could flow in reverse, a layer of threads inside the pipe snapped shut like a valve, blocking any backflow.
"Individual Artoria can keep pumping that fluid, I will manage the backflow." Irisviel declared from the laptop.
Artoria whipped her head toward Irisviel and glared at her as well. The Einzbern looked back, her expression unmoved, save for a half-second delay, as if searching for what the glare was about.
"Get to work, we still have three other tubes to drain and fill after this."
Shoulders going slack at my words, Artoria brought her focus back to her task.
"I will get it done, Master."
A short, frustrated sob escaped her, caught halfway and swallowed before it could finish.
I ignored it.
She'd asked to contribute, and this was what contributing looked like.
...
..
.
***
[200 Power Stones = 1 Bonus Chapter]
[15 chapters ahead on P@tr3on = [email protected]/Not_Aaryan]
...
[Author's Thoughts]
You all understood the explanation, right? I tried to make it as simple as possible, you can ask me in comments if you didn't, I don't mind explaining it again.
And good news for everyone, Mommy Artoria might be coming sooner than expected!
Ultimate Talents used in this chapter. - [Ultimate Mechanic], [Ultimate Inventor], [Ultimate Analyst], [Ultimate Swordsman], [Ultimate Teacher].
[Ultimate Teacher] is the one buried deep underneath everything else. Do you all feel it yourself? Most probably could but didn't think in that direction at all.
Anyway, have a phenomenal day, everyone!