A Mastermind? No, I'm just the Live-In Son-in-Law-Chapter 7: Oath

She had become something more hopeless and wretched than a commoner—less than even a lowborn serf—fated to plummet endlessly into ruin.

And that truth was hammered into her each time she was sold off like defective stock at half price in the slave markets, each time she swept northern town dust wearing the uniform of those who used to serve her, each time she was summoned to her master's room before dawn as if it were her duty.

She was no longer Lunelle Misthylene, proud knight. She was now item number 167, a slave-market product—an ornamental beauty fit to be displayed.

From now on, there would be no sword in her hand, only brooms and rags. No more knight’s vows—only a life lived catering to her master’s whims.

Yes... that’s what she had thought—

***

“Haah...!”

Lunelle gasped and snapped her eyes open, instinctively pushing herself upright.

“Hah... hah...”

She had just come to after passing out, and her mind was still foggy.

Though the excruciating pain from earlier had faded, her entire body ached with unforgettable agony, and her sweat-soaked clothes clung to her, weighing her down.

She couldn't even sit up fully. For a while, she just panted heavily, glancing around, until she finally realized she was lying alone in a corner of the basement.

“Ah...”

Her dazed expression lingered as the image of Whitney’s disappointed gaze flashed in her mind—along with his mutter that she had fallen short of expectations.

“...So it failed.”

Considering all that, it was likely the ritual had failed. She’d lost her value, and now she’d simply been left behind here.

“...?”

But as she bowed her head in resignation, her eyes happened upon a single piece of paper lying on the floor.

She picked it up—the ritual had knocked her unconscious, so she hadn’t seen it before—and her gaze scanned the neat handwriting.

And then her body froze, as if time itself had stopped.

“The ritual was a success.”

That line, clearly written in Whitney’s hand, hit with overwhelming force.

“Of course, your body hasn’t fully recovered yet. You’ll likely have to endure pain like this several more times.”

Though Lunelle had collapsed from the shock of mana overflow, her body showed no lasting damage beyond lingering soreness.

“But, as of today, you should be able to wield mana again.”

Her eyes stayed locked on the paper, «N.o.v.e.l.i.g.h.t» and her hand began to tremble.

“Once you’ve rested, please come to my office. We’ll continue the conversation then.”

And at the very bottom of the note:

“Congratulations on being able to hold a sword again, Miss Lunelle Misthylene.”

The note slipped from her trembling hand, landing softly on the floor.

P.S. The front door of the basement isn’t locked, but please use the back door connected to my office if possible.

She never even saw the small, friendly postscript—her mind was already somewhere else.

—Step, step...

Without even glancing at the note again, Lunelle began staggering forward.

The words “You can hold a sword again” were ones she’d heard many times before from conmen and charlatans—but this time, something was different.

As the seconds ticked by, she began to feel it clearly: a change in her body, faint echoes of her former brilliance.

But “feeling” wasn’t enough.

After all these years of crawling through hell, after dreaming of this moment every night, she couldn’t rest until she saw it with her own eyes.

“I have to confirm it... right now...”

Mustering what little strength remained, she opened the long-neglected front door of the basement and stumbled forward.

The passage, untouched for years, was thick with dust, damp, and cloaked in darkness. But thankfully, a faint light shone at the end—an exit, most likely.

It was no more than a small, thin, sliver of light.

But to Lunelle, trapped in the dark for so long, that faint glow was blinding.

—Creeaak...

Almost moving unconsciously, she reached the end of the passage and pushed up with all her remaining strength.

Brilliant sunlight, incomparable to anything before, flooded her vision.

“Ah...”

She winced slightly at the brightness, emerging into the open—and quickly realized she was standing in the middle of the Ringaarden estate’s garden.

“Eek—!”

“Wh-Who...?”

The gardeners tending the flowers and the maid fetching water nearby stared at her in shock.

But Lunelle didn’t care. She immediately began scanning her surroundings.

Her clothes were in tatters, soaked with cold sweat and stained with dirt and blood. The metallic stench of dried blood clung to her.

“Isn’t that the girl? The one the young master brought in last week—?”

“I-I saw her leaving her room before dawn yesterday...”

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She looked like someone who’d barely survived a horrific ordeal, and the maids watched her with deep concern—but Lunelle’s focus was elsewhere.

“Where... where’s a sword?”

Right now, her mind could think of nothing but grabbing a blade.

Her instructor had once told her: when a knight leaves for duty, the training hall is locked. The estate’s armory could only be accessed by authorized personnel or the quartermaster.

Which meant there was only one place left where she might find something—anything—remotely sword-like.

“W-Where’s she going?”

“S-Shouldn’t we follow her?”

Realizing her destination, Lunelle staggered toward the mansion. The maids, alarmed, followed close behind.

“W-Wait, please—!”

“Move.”

A few tried to stop her, but she met their eyes with a cold, razor-sharp glare—and they instinctively shrank back and let her pass.

“Yes... it should be here...”

At last, Lunelle reached her destination—none other than the weapons storage room.

Trailing her unwitting entourage, she stepped inside, eyes scanning the room in a haze.

“...Found it.”

And the next moment—before anyone could stop her—Lunelle’s hand reached out toward a small utility rack near the entrance.

—Srrrng...

Her fingers closed around the hilt of a sharp kitchen knife.

The maids who had followed her inside all froze on the spot.

“...Ha.”

And then, after who knew how long—

“...Hah... hahahaha...”

The icy silence that had settled in the kitchen was finally shattered by a sound no one could believe came from Lunelle’s mouth—a chilling laugh.

“Ahahahahahahaha!!!”

While the others remained frozen in place, overwhelmed by the manic laughter, Lunelle sank down to the floor, as if her legs had finally given out, still clutching the kitchen knife in both hands.

“Haha... ha... hahaha...”

Her twisted expression was unnerving, yet the corners of her mouth curled upward in pure ecstasy, and tears streamed down her cheeks as she laughed like a madwoman.

“Whitney Ringaarden.”

Her cracked, hoarse voice echoed softly from her lips, and the stunned bystanders all flinched.

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But none of them dared to approach the trembling woman on the floor.

“If this is the price I pay for selling you my soul...”

Thanks to that, no one noticed the faint, glimmering sword aura emanating from Lunelle’s back—an aura that barely shimmered within her grasp, clinging to the small kitchen knife.

That pale, flickering glow was just like the light that had poured into the basement corridor—a fragile thing, ready to vanish at any moment.

But to Lunelle, it was the very hope she had wished and prayed for over so many long years.

“...then I will gladly become your hand.”

If she could see it again—if she could hold a sword once more—she would offer up her soul without hesitation.

“...Come to think of it, didn’t I hear screaming last night~?”

“S-So... that wasn’t a stray cat...?”

“Shh. We don’t know anything.”

Of course, the maids—unaware of the grim context—let out sighs of relief as Lunelle finally set the knife down, awkward laughter trailing behind her fading grin. They would soon begin spinning the story of the “kitchen knife incident” into an exaggerated rumor.

“I didn’t hear anything... I didn’t see anything... I didn’t...”

The librarian, who had been quietly making sandwiches alone and dove under the counter the moment things got weird, now had tears welling in her eyes—but there was no one to correct the misunderstanding. That ship had sailed.

***

Whew... I almost died from shock.

Rubbing my suddenly itchy ear as I sorted through paperwork in my office, I shivered at the memory of the pain from just a few hours ago.

I thought I was used to pain, but that was beyond anything I expected.

Sharing Lunelle’s pain was incredibly stupid, in hindsight. I’d almost ended up with a game over.

Then again, forcibly opening a mana channel through someone’s soul should probably hurt that much.

Still, thinking about having to share that pain several more times... I could only sigh.

Well, it is what it is.

Considering the future events I still had to survive, the deal was more than worth it.

And honestly, as someone who’d just unlocked a route that nobody else had ever cleared, I couldn’t help but feel a serious sense of accomplishment.

Yeah, it sounds like something only a hardcore gamer would say—but hey, this was my reality now, so I had no shame.

Besides, 8,500 hours of total playtime doesn’t really make you an addict, right?

—Knock knock knock.

“...Come in.”

Still spacing out, I turned back toward the mountainous pile of documents on my desk—just in time to hear a knock at the door.

Alfred, I swear, if it’s more paperwork—

Naturally, I expected it to be Alfred. I was all set to grumble about the ever-growing workload when the person who walked in... wasn’t him.

It was Lunelle.

Her gaze was sharper than it had been all week—surprisingly so, considering the lingering aftereffects she should still be dealing with.

I, for one, was still sore all over. My muscles felt like they were on fire.

Has she already recovered? She could’ve rested longer if she needed—

“I have a question.”

I was about to express my concern, but her quiet, composed voice cut me off.

“What do you want from me?”

The seriousness of her expression threw me for a moment—but the question itself was a simple one.

Well, what I want is a dream team of busted characters who were impossible to recruit in the game, people strong enough to guarantee my survival and peace of mind.

And since I’d secured Lunelle—the bare minimum needed to start building that team—I’d already gotten what I wanted.

“If it’s what I want... then I’ve already got it.”

I smiled as gently as I could, looking her in the eyes as I spoke.

She didn’t respond. Just stood there, staring silently at me.

“Honestly, I’m in kind of a risky position right now, so I need reliable protection—”

“I understand.”

Before I could even finish explaining, Lunelle suddenly interrupted with a voice full of certainty.

“Then, I will make my oath.”

“...Excuse me?”

Before I knew it, she had dropped to one knee, bowed her head, and spoke in a solemn tone.

“To my enemies: judgment and punishment. To my lord: mercy and loyalty. I shall uphold honor and faith, and maintain pride through hardship.”

Wait—hold on. That’s the Knight’s Oath, isn’t it?

“I, Lunelle Misthylene, vow to bring only victory and glory to my liege.”

I mean, I get that she was once broken and is now back on her feet, but she’s seriously reciting the oath—the oath—without even hesitating?

“From this moment forth, Whitney Ringaarden...”

Lunelle slowly raised her head, her gaze locked on mine.

“...I swear to become your loyal blade and faithful tool.”

Of course, having Lunelle swear loyalty to me was great news.

The Knight’s Oath can’t be coerced—it must be made of the knight’s own volition. And once sworn, it’s unbreakable, binding the oath-taker to absolute loyalty for life.

Moreover, those who swear the Oath become, in a legal sense, property. Their mana becomes bound to their liege.

That’s why it’s jokingly referred to as “becoming a knight-slave” at least once in every noble circle.

But here’s the problem.

Because of that “mana binding,” anyone capable of sensing mana will immediately know that Lunelle now belongs to me.

Her recovery isn’t complete, and with everything coming up... It would’ve been better to keep her resurgence hidden.

I mean, I was going to ask her to make the oath later, after everything was settled and her body was fully restored...

“Uh, actually, maybe you could wait on that—oh.”

I tried to stop her in a panic, but I was already too late.

She’d finished the oath.

Did... did she take my earlier answer as acceptance? Did our mana just synchronize automatically because of that?

Damn it. This is why you’re supposed to watch your mouth during contracts and rituals.

Lunelle smiled faintly.

There was something subtly decadent about that smile—but I didn’t have the brainpower to analyze it right now.

“For now, please stay indoors and focus on recovering. I’ll figure out the next steps—”

“Y-Y-Young Master!”

And just as I was preparing to manage the aftermath...

“L-Lady Meredia says she wishes to see you...!”

“...Oh boy.”

The panicked librarian stammered out the news—Meredia was requesting an audience.

“Perfect timing. Let’s go ahead and schedule something—”

“S-She’s already waiting in the garden.”

“...We’re screwed.”

I never really expected everything to go smoothly, but come on—this is just cruel.

The only silver lining here is that the final boss, the one who could erase me with a snap of her fingers, doesn’t currently bear any hostility toward me.

“And... she said if you don’t have a convincing explanation about those documents from last time...”

“Yes?”

“...you’d better be prepared for the consequences...”

“...Miss Lunelle, shall we take a walk in the garden together?”

To hell with it. I give up.