Achilles' Heel

A full moon hung low in the dark night.

In the Imperial University library, Yeriel was secretly studying magic.

Lately, staying in Hadekan had started to feel burdensome for no good reason, so she'd come down to the capital for a bit.

The cause was, of course, the Altar's raid on the imperial palace.

These days, every single day was a nail-biting ordeal for Yeriel.

Of course, no one dared demand a bloodline verification from a Yukline, but that was only "for now."

"...Whew. The rest can wait."

Around 10 p.m., ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠she wrapped up roughly and shuffled out to the university athletic field. Naturally, there were plenty of shadowy escorts hidden nearby.

Given the state of the world, after all.

"Hm?"

On her way back to Deculein's mansion, Yeriel suddenly spotted some mages.

Ifrin, Maho, Drent, and the rest of the "Plain Magic Exploration" club members.

—But how do we make it safe? Anyone got ideas?

—Dunno... Ifrin, can't we just make it sturdy?

—Then it won't fly. Too heavy.

—Add lightweight enchantment?

—Gets too expensive.

They were chattering around some busted contraption in the middle.

Yeriel approached out of curiosity.

"What're you punks doing?"

"Oh? Ah~ Lady Yeriel."

Ifrin beamed and waved. Yeriel narrowed her eyes.

"How many times I gotta say it's 'senpai', not 'lady'... Whatever, what the hell are you up to?"

"Power engine. Prepping our expo entry."

"Oh... that? A power engine?"

A wrecked power engine. Too round for a plane, no wings, and some propeller on top.

"Thinking of naming it 'Helicoptercio Sauron Mister Sparta' or something."

"Sounds good? Too damn long. But why struggle alone? Ask Deculein for help. He's your advisor, right?"

Even as she said it, Yeriel clutched her skirt hem in secret.

She couldn't get close to Deculein.

Couldn't act friendly or nice.

To the world, they had to look like they hated each other—really hated each other.

Because she was Deculein's deadliest Achilles' heel.

"Doubt it'll work. Prof's been busy lately."

Drent spoke up. Ifrin chimed in.

"Yeah. Showed him this, got totally roasted. Fixing it now, but..."

Anyway, it's tough. No help from him.

Ifrin sighed, staring at the stock certificate in her hand. Soon, a sly grin crept onto her face.

"Heh heh... I'm rich."

Ignoring the muttering Ifrin, Yeriel mustered some courage. She glanced up at the towering magic tower.

77th floor—Deculein's office was still lit.

Yeriel said,

"Fine. I'll talk to him."

The Plain Magic Exploration members' eyes went wide. Ifrin asked,

"For real?"

"Yeah. We may hate each other's guts, but I can chat easier than you lot. Got stuff to say anyway."

"Whoa! Thanks!"

Yeriel smirked and turned.

She headed straight into the tower and boarded the elevator.

"Hoo..."

Ding!—

Deep breath, and she arrived at the 77th floor.

—...If you're talking about Yeriel.

Deculein's voice leaked from the office. Tense mana pulsed in the dark hallway.

Yeriel instinctively cloaked herself and peered around.

Through the half-open chief professor's office door, light flickered. And there were two presences.

Deculein wasn't alone...

—That child isn't even worth using as a bargaining chip.

...30 minutes earlier.

In the chief professor's office, I'd reached a certain Understanding of Dikailen's art magic.

To sum it up in one line:

'Worthy of being called a masterpiece theory.'

Dikailen's magic, built on engineering, science, biomechanics, and magic studies, literally enabled the creation of 'living, moving magical artworks,' and it meshed excellently with other magic lines.

While most magic theories were like 'pure mathematics' such as geometry or analysis, this was closer to practical art.

"However..."

The catch: It used demonic energy as its medium, the biggest hurdle.

If it could output similarly with mana, it might become the ultimate goal for refinement mages—a light and salt unto them.

"Not impossible."

Right now, I was onto a clue for that method.

"Refinement, though."

Even among mages, 'line discrimination' existed, and refinement was heavily looked down on.

Historically, before Dikailen, refinement specialists were called 'technicians'; only after did they gain recognition.

Even now, among Ether-rank mages, only Roserio was refinement.

Dikailen's extremely twisted personality probably stemmed partly from that.

"Need a curriculum."

With the main quest looming, no need for knowledge hoarding anymore.

I'd scout as many talents as possible and grow them fast. Getting greedy and dooming the continent? What greater shame?

Thus...

Whoooosh—

Then, wind rushed through the window. But I hadn't opened it, and the intruder knew that.

I sneered at it.

"...Altiegue of the desert."

The sudden uninvited guest, the desert's second leader.

The woman with a hefty bounty on her neck—Elesol—signed.

"Why come here? Don't value your life? Or is Eli nearby?"

"Promise? The Rohalak gas chamber?"

Elesol grimaced. She signed roughly, mana flaring.

"..."

My expression hardened. I straightened without a word.

Chin up, I glared down at the insolent Altiegue.

"...If you're talking about Yeriel."

"That child isn't even worth using as a bargaining chip."

I seized Elesol's moving hand with Telekinesis. She froze like a statue.

"I say again: If you have any hope, it's that child. Do not even think of folly."

"Hup!"

Her kiai disrupted my Telekinesis with released mana.

A decent Altiegue, after all.

"Deaf-mute, yet you shout well."

She signed delicately.

Each word precise.

"..."

I stared silently.

A smirk escaped.

Pathetic threat.

"Yeriel. That child is my sister before any Altiegue."

"If scum like you threaten her safety, I swear—by the ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠name of Yukline—I shall exterminate your kind."

Night's darkness flooded the office.

Elesol showed no reaction. Just sighed with a blank face.

The answer to that trivial question was obvious.

No need to deliberate.

"Even unto ruin."

Elesol closed her eyes briefly.

As if pondering, then nodded with a wry smile.

"Yuren?"

I furrowed my brow slightly.

"Intel was the goal from the start?"

"Hmph. Not brainless. Then, their goal?"

That one line revealed Altar's aim.

"The volcano."

Yuren was crucial for the Mieolji expedition and main quest endgame.

Early destruction would make game clear impossible.

"Fortunate. Lately studying refinement magic."

"Hmph. Mysteries beyond your kind's ken abound."

Elesol frowned but soon shook her head, signing.

I nodded.

She paused, eyes on me.

Then, with trembling signs, asked her doubt.

I answered instantly.

No deliberation needed.

"Simple. Yeriel is Altiegue, but Altiegue is not Yeriel. Or are you Yeriel now?"

Cold wind brushed again. Elesol's hair swayed.

Soon, she smiled and nodded firmly.

With that sign, she leaped out the window, vanishing.

"...But do not misunderstand."

Altiegue. The world's most complex clan.

"Leader of the Altiegue."

Whether they heard or not.

"I do not hate you. Pity and contempt, merely."

I rose, opening the office door...

"..."

Dark hallway. Moonlight seeped in, illuminating water droplets on the floor.

Clear, glistening moisture.

Proof someone had been here moments ago.

"Tch."

Of course, my Iron Man senses faintly caught the presence.

Thought it was Elesol's guard, so I let it be.

"...Yeriel, was it."

I silently watched those ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠tear stains.

...Three days later.

In the VVIP cabin of the airship to Yuren.

I glared at the formulas on the magic paper. Also pondering a letter to Yeriel.

Both brain hemispheres at work.

"Tch."

Both sides tough.

What to tell the crying sister that night? This damned 'conversion formula' too.

How to solve it?

"Professor. What's that?"

Suddenly, Ifrin beside me showed interest. She'd been sneaking peeks.

"Conversion formula."

"Eugh... Looks super easy?"

"...Easy?"

How to deal with this impudent fool. Flick her forehead? Or words?

"Then this is hard?"

Well, it looked simple superficially.

Just one or two lines; as math, deceptively basic.

Roughly, just three independent equations like that.

"Converting what? What's A, B, C?"

"Relation between demonic energy and mana I'm seeking. Similar forces, same 'origin,' hence simple conversion."

"Hmm~ Gimme. I can solve it."

Ifrin snatched the paper.

"Lemme see..."

I glared, shook my head.

...15 minutes later.

"Sneaky tough, huh? Still looks easy."

Ifrin, clueless as ever.

To this idiot, I showed half the solution.

"Take it. Finish."

"Huh? I think I can too... Um. What's this say?"

Her eyes bulged at the solution.

I sneered.

"Two heads better than one. Ponder while looking."

"..."

Problem one line, solution hundreds of pages.

No—unfinished, so more.

"Mobilizes all math—magic rituals, functions, geometry—to posit 'void mana,' a 'mana-neutral state.'"

Ifrin gulped.

Did she think converting demonic energy to mana easy?

"What looks easy is often hardest."

"Aha... But a theory even you can't solve?"

I shrugged.

"Verification takes too long. Rough ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠formula, eliminate errors—might be easy. But each check: 3 months."

"Experiment method?"

Nosy now, but curiosity is mage's virtue.

"Inject mana via formula into demonic mana stone, wait 3 months for result. Now shut up."

I refocused on the solution.

Airship still en route to Yuren.

But.

Tap tap.

Ifrin poked my shoulder again. I glared.

"Ifrin. Fancy skydiving? Right now."

"Huh? No. This."

She pulled her pocket watch.

"One more use. Watch."

Placed a cookie crumb on it, infused mana.

Instantly, hour and second hands spun wildly.

Tick-tock-tick-tock-tick-tock—

Ifrin eyes closed; my lips curved into a smile.

About 30 seconds later.

"...Whew! How's that?"

Ifrin proudly lifted the cookie. I examined closely.

In mere 30 seconds: moldy beyond eating, crumbling to dust.

Result of 'time travel.'

"How far future?"

"Exactly 3 months. Piece of cake."

Ifrin crossed arms, nose high.

To this rarely cute fool, I said,

"...Finally something useful."

"Heh heh hew!"

Then, flap—formula paper and solution fluttered under the seat.

Next, the magic paper itself vanished empty.

Obviously, magic at work.

"Whoa! What!"

Ifrin reacted first.

"No!"

I stayed calm, but she bolted up, yelling.

"Damn it, thief! Here! Thief! THIIIIEEEEF—!"

VVIP held thirty. Her scream drew frowns our way, but thief or not, irrelevant.

"Sir, please calm. No thieves in VVIP."

"There is! Magic-snatched it! Ah, I didn't learn Reverse Trace harmony. What now? Professor knows?"

"...Ifrin. Shut your mouth."

The formula itself was nothing special.

Even knowing paper and solution, unsolvable—

"No, Deculein Professor's new magic theory stolen! Unreleased theory, swiped whole!"

"What? True?!"

Attendant gawked at me.

"..."

Silently, I pictured tomorrow's headlines.

"Nearly 100 million elne value—no, 100 million? 10 billion elne!"

"Impossible!"

And the airship blared alarms.