A Mastermind? No, I'm just the Live-In Son-in-Law-Chapter 26: The Princess and the Saintess

“...I did it.”

Soaked with sweat, she panted heavily—but a proud smile crept onto her lips, one she couldn’t hide.

“I think I’m finally getting the hang of sword energy.”

Yes. What she had just accomplished was the projection of materialized sword energy.

It went beyond merely coating the blade with aura to enhance its sharpness—it could slice from a distance, even where the blade didn’t reach.

Essentially, it was the pinnacle of all commonly known sword techniques.

Naturally, the difficulty was extreme. Not just aspiring knights, but even seasoned swordsmen with decades of training often failed to manifest their own sword energy and gave up in frustration.

To surpass that wall before even graduating from the Academy—and to be refining it independently—Cecil’s talent was surely among the finest in the Empire.

“...Hey.”

She was aware of that fact to some degree—and even took pride in it.

So when a voice suddenly interrupted from beside her—

“That’s not how you use sword energy.”

“...?”

Still seated, Cecil could only doubt her ears.

“You gotta tighten your core right here! And then do it like bam-bam-pow!—that kind of feeling!”

“Huh?”

Frowning, she turned toward the source of the voice—puzzled by the sight.

“Who... are you?”

The blond-haired boy beside her, speaking with such authority, was someone she had never seen before in the mansion.

‘He looks... kind of familiar though...’

“Ah.”

But the moment her eyes narrowed in suspicion at his vaguely familiar appearance, the strange boy flinched and clammed up.

“Uh, well... I mean... I’m, uhh...”

Rolling his eyes nervously, he stammered.

“I-I’m Sir Whitney’s close friend? I was just invited here and arrived just now.”

“...Friend?”

“I-I’m with the Imperial Knights! You can tell from the uniform, right?”

He pointed awkwardly at his uniform, flashing a strained smile.

“Anyway, that’s not how you use sword energy. Your technique’s so inefficient you’ll wear yourself out in no time—”

“If you know so much...”

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Cecil’s eyes lit with defiance as she rose to her feet and thrust her sword toward him.

“Then why don’t you show me?”

“Hmm, sure!”

Without hesitation, the boy took her sword, then—

“Hup—”

He exhaled briefly and swung it lightly forward like a bat.

—BOOOM...!

To her shock, the arc of sword energy he released roared through the air and tore far across the mansion courtyard.

“W-what...?”

“See? You just do it like bam-bam! then whoosh! Easy, right?”

“......”

As he waved the sword around casually and babbled in nonsense-speak, Cecil bit her lip and quietly growled—

“Try it on me.”

“Huh?”

“You never know. Maybe it just looks impressive but lacks real weight.”

Despite witnessing the arc herself, she picked up a spare training sword and challenged him with reckless provocation.

“Really? Then prepare yourself! Nothing proves a technique better than a direct clash!”

The boy smiled brightly and readied his stance without the slightest hesitation.

—BOOM!

In the next instant—

“Kh...!”

Cecil tried to block the blow with her own sword energy, but the force overwhelmed her—knocking the blade from her hand and sending her flying across the dirt.

“Are you alright?!”

“...Again.”

Though tossed to the ground, Cecil gritted her teeth, pushed herself up, and demanded another attack.

“Just once more...”

“Good! I like your spirit! Alright, here I go—”

The boy raised his sword again, full of energy, preparing to swing—

“That’s enough. I think the match is over.”

“Ah.”

Suddenly, Whitney appeared, grabbing the boy’s wrist and declaring the duel finished—his expression completely devoid of his usual smile.

“Cecil.”

“...Nngh.”

“What were you going to do if you got hurt?”

He scolded her softly as he glanced at her dirtied figure. Cecil, trembling and biting her lip, looked up in protest—

“My little sister is the future head of our family, after all.”

“......”

“You can’t be disappointing your big brother so soon, can you?”

Faced with Whitney’s calm, terrifying presence and cold smile, Cecil quietly lowered her head and muttered—

“...Sorry.”

“That’s all I needed to hear.”

Of course, Whitney hadn’t meant to unleash that aura—it was purely out of concern. Hearing her apology, his tension eased, and his face warmed with a gentle smile.

“Really, you’re too kind for your own good, Cecil.”

“R-really?”

“You’re at that rebellious age, you know? You should be talking back to me more. But you always shrink whenever I’m around. I wonder why that is...”

He smiled, trying to be affectionate—but the boy, still pretending to be Whitney’s friend, could no longer focus on his words.

“I—I think I know why...”

“Hmm?”

“...N-no, it’s nothing.”

He had to swallow his words with every ounce of willpower—because anyone would break into a cold sweat with Whitney glaring like that, even if it was just gentle scolding.

“Oh, and Your Highness—please be more careful from now on.”

“Huh?”

This translation is the intellectual property of Novelight.

“If Cecil gets hurt even once more, I might have to end our friendship.”

“Eek. G-got it!”

The boy nodded furiously, wearing a stiff smile.

“Anyway, Cecil, don’t be discouraged.”

Still unaware of his own fundamental problem, Whitney turned toward his little sister with a low voice, offering comfort.

“From where I stood, you held up pretty well.”

“......”

But for Cecil, whose pride had just been shattered by an anonymous knight, those words didn’t help at all.

“Only one person in the Empire can withstand His Highness’s sword energy head-on—and that’s Sir Lunelle.”

“...What?”

Whitney whispered this even softer, and Cecil’s stunned expression shifted as she finally caught on.

“Wait... then that boy is...”

“Shh. He’s in disguise. Pretend you don’t know.”

Only then did she realize: the boy she had just crossed swords with was the first in line to the Imperial throne.

“Well, I’ve got to go have a little chat with His Highness.”

Patting her frozen shoulder gently, Whitney turned and walked off with the prince.

“Shall we head inside, Your Highness?”

“Ah, y-yeah. Sure.”

“I’ve prepared the reception room for you. Haha...”

Watching them go, Cecil stood frozen, dazed.

“He became a hero overnight... and now...”

She dropped her sword and mumbled helplessly,

“...he’s friends with the prince?”

Contrary to Whitney’s intent of reassuring her—revealing the truth only made her feel even more distanced from the role of family head.

“...Seriously, that’s terrifying.”

The seat of head of house, which had already felt out of reach, now felt impossibly far away—and in her fiercely determined eyes, tears quietly welled up.

***

“Huu...”

Just barely managing to drag Prince Kendrick—no, Princess Katarina—to the office before she could end up in a life-or-death duel with Cecil, I sank back into my chair with a deep sigh.

“U-um... Sir Whitney. About earlier... I’m sorry.”

“......”

“W-we’re still friends, right?”

She hesitantly asked from beside me, voice shrinking. I paused to stare at her for a moment.

“Yes, we are.”

“Ah! Thank goodness!”

“But... why are you sitting right next to me instead of across from me?”

I’d been curious about it ever since she sat down, so I finally asked.

“W-well, isn’t this what friends usually do?”

Her wide-eyed response was so unexpected that even I, who had steeled myself for just about anything, felt a wave of dizziness.

“...Your Highness.”

“What is it?”

“I mean this with the utmost respect... but have you perhaps never had a friend before?”

“U-uh... w-well... not really.”

With that, she visibly deflated, mumbling out the truth.

“I-it’s just... if I got too close to a guy, my secret might slip... and for some reason, the noble ladies never wanted to be friends with me either...”

“But weren’t you close with Sir Maier?”

“H-he was more of... a close aide than a friend.”

She added in a small voice, “Not anymore, though,” and her expression darkened. I resisted the oncoming headache and made up my mind to console her.

“Well, actually, I’ve never had a friend either. So I understand.”

“Ah, really?!”

“Still, it’s a bit overwhelming to have Your Highness seated beside me, so I’ll move to the other side.”

Of course, I wasn’t planning on sticking to her side forever, so I rose from my seat—only to see her briefly brightened face turn gloomy again.

‘Wasn’t this the same person who split the training ground in half with sword aura earlier...?’

Lunelle was the same way—are all sword geniuses slightly unhinged?

Katarina was especially infamous for being a complete lost cause.

If she had even half the intelligence to match her sword skills, the entire course of the game might have played out very differently.

“Anyway, the reason I invited you here today, in confidence, is—”

“B-before that! I have to ask something!”

Just as I was getting to the point, Katarina suddenly interrupted, visibly anxious.

“H-how did you figure out... that I’m actually a girl?”

“I-I’ve worked so hard since I was little, you know! Cutting my hair short like this, trying to speak in a deep voice...”

Sorry to say, I’d figured it out through bluffing—based on the narrative clue that she had a hidden weakness.

And the only reason it worked was because her hair was practically white, which was a major giveaway.

“Was it... my body shape!?”

“...Body shape?”

I was still trying to come up with an excuse when she suddenly raised her voice, eyes wide.

“L-like, maybe my waist and arms look slimmer than other boys? Or maybe it’s the curve of my hips—”

“That’s not it.”

Dear gods. Is she trying to get me executed for harassment?

“Then—was it the chest binding coming loose?!”

“Oh no.”

“Now that I think of it, my chest has been feeling more compressed lately!”

Before I could stop her, Katarina yanked open her uniform and revealed the chest bindings underneath.

“I always check them multiple times before going out! This really is strange...”

“...Let’s save this conversation for later, shall we?”

Closing my eyes and turning my head aside, I replied as calmly as I could.

“Please, Sir Whitney! This is a matter of life and death for me!”

“If you cooperate with me on this matter, I’ll tell you.”

“...Ah! Deal! I’ll give it my all!”

Well, at least she’s obedient. It’s no wonder everyone treats her like a pushover both in and out of the game.

“So... what is it you want from me this time?”

“Ahem. Yes, what I’d like to ask of Your Highness is...”

Seizing the moment, I smiled brightly and lowered my voice:

“Appoint me as a judge for the upcoming Promising Newcomers Tournament at the Academy.”

“Hmm. That’s not hard to arrange... but why?”

She tilted her head, asking with innocent curiosity.

“Haha, well...”

Staring directly at her, I replied meaningfully:

“Because I need to take the saintess there. Only then can I complete my plan—and save Your Highness as well.”

“R-really?! Then of course I’ll help!”

I didn’t explain what the plan actually was, but she nodded so hard it looked like her neck might snap.

‘...I feel kinda bad about this.’

But honestly, even if I begged her to keep it secret, she’d probably spill the plan anyway.

In that sense, I was actually doing her a favor.

“But do keep in mind—if you go through with this, Your Highness will lose your fiancée.”

“T-that is... hmm...”

Guilt creeping up on me, I decided I should at least share that much.

Even if they weren’t destined to marry, politically speaking, it would be a major blow.

Once the saintess meets one of the playable characters, her fate will be to walk the path of saving the world—making the engagement impossible to maintain.

‘Especially if the playable is male, it’ll be over for sure.’

Of course, I doubted Katarina had proposed out of love. There were surely political reasons tied to it. Better to be upfront.

“...If it helps, would you like to say your goodbyes in advance?”

“U-umm...”

“Haha, no rush. Take your time to—”

Just as I tried to reassure her—

—CRASH!

The sudden sound of shattering porcelain rang out.

“Ah? Oh no, I messed up again... huh?”

Katarina instinctively glanced down with an apology, but—

“Hmm.”

I’d specifically removed all breakable objects from the table for just this kind of situation. Frowning, I turned toward the door.

‘...Did Sasha mess up again?’

She was probably trembling in panic already. I figured I’d give her some comfort—and give Katarina time to think.

***

“Haha, Miss Sasha. Please don’t worry about it.”

Muttering as I opened the door, already planning how to cover for Sasha’s blunder again—

“Actually, ever since last time, you were automatically enrolled in the staff accident insurance program I designed—huh?”

But the one crouched on the floor, surrounded by broken teacups and plates, wasn’t Sasha.

“Haa... haa...”

“...Well, this is unexpected.”

Lady Hestia—who was supposed to be cleaning my room—was sitting against the wall, legs collapsed under her, face pale and breathing heavily.

“This is... troublesome.”

“I-I was just... just passing by...!”

The moment her dazed, trembling eyes locked onto mine, she stammered in a panic.

“So.”

Kneeling in front of her, I leaned in and whispered calmly.

“How much did you hear?”

Like Katarina had thought earlier... my gentle voice and cold, murderous smile contrasted just enough to—

‘I’m gonna die I’m gonna die I’m gonna die I’m gonna die—’

It was more than enough to make the saintess’s heart feel like it was about to explode.

‘W-what exactly did I hear?!’

And to be fair... my own heart was pounding just as violently as hers—like it, too, was being carved open with a blade.