Manaka Sajyou's POV
When Father and my brother sat talking at the breakfast table, I cast an illusion to make it look like both I and Hassan of Serenity were still sitting there, exactly as my brother had instructed.
Meanwhile, I slipped away to search for the Caster and take him as our subordinate.
The truth was, Hassan of Serenity wasn't actually my brother's Servant. She was mine.
I was the one who held her Command Spells, not on the back of my hand, but on my chest, shaped like a red tattoo etched right over my heart.
My brother liked it that way.
In fact, he often stroked that mark with his fingers whenever we were having sex, his touch more possessive and eager than usual, like he took pride in knowing she belonged to me.
To everyone else, though, it was a firmly established "fact" that Assassin belonged to my brother.
Hassan of Serenity was kept in the background, playing the part of a passive observer instead of an active participant.
According to our current plan, my brother pretended he had no real interest in the Holy Grail War at all.
He stayed home, acted detached, and refrained from attacking anyone, always appearing calm and harmless with Assassin lingering silently nearby.
He even went so far as to tell Saber that he fully supported her and Father in winning the Holy Grail War and that if it came down to it, the final result should be decided through an honorable duel between Hassan of Serenity and Saber.
Saber didn't suspect a thing. Father didn't either.
Everyone was happy and blissfully ignorant of the truth.
But of course, that wasn't the point.
The most important thing was that Caster's Master was Misaya's father and she was the obstacle I needed to erase to keep her from getting in the way of my brother's full affection.
I hated the way he'd flirted with her in the library before, the way he'd smiled at her and even gifted her the ability to summon the Queen of Shadow.
She needed to die.
Unfortunately, as if she'd somehow sensed exactly what I intended, she had vanished from this world completely, taking the Queen of Shadow with her.
Left with nowhere else to vent my fury, I turned my attention to the man closest to her, the one who'd fathered that bitch, Aritoshi Reiroukan.
The man's eyes flew wide open in shock as his body seized up, paralyzed by the lethal poison that Assassin had slipped into his veins.
It wasn't even the poison that truly terrified him, it was the sight of Caster, standing obediently behind me like a loyal servant, gazing at him with cold, unblinking eyes.
Aritoshi's lips trembled as he tried to form words, but all that came out was a strangled, wet gasp.
And in that moment, the look in his eyes was delicious, pure disbelief and horror as he finally realized how completely the tables had turned.
"Caster, why? Why are you betraying me?" he demanded, anguish and raw pain twisting his face.
His body was paralyzed by poison, leaving him helpless to do anything but watch the betrayal unfold in front of his eyes.
Caster let out a weary sigh. "I apologize, Master. But as a magus, have you forgotten the most important pursuit in our lives?"
"She is our ultimate pursuit. And it should be your honor, Master, that she has willingly come here and decided to take matters into her own hands, for your sake," he added, his voice shifting into a fanatical fervor as he glanced at me.
He cleared his throat, realizing he'd lost his composure, and resumed his usual cold, calm demeanor.
"Do you intend to at least hear her out first, Master? Perhaps she might be merciful enough to grant you a shred of mercy," he continued.
Aritoshi Reiroukan snorted, his voice dripping with icy disdain. "I recognize you, girl. You're Hiroki's daughter. Your brother often played with Miyaka. We never wronged you or your family. Why the hell are you doing this to us?"
I hummed softly, an amused, mocking sound. "Are you in first grade, old man? This is the Holy Grail War. You either win… or you die."
I tilted my head, my eyes glinting coldly. "Besides, I've got no immediate plans to kill you, old man. But your daughter… well, that's another story."
A dark chuckle slipped past my lips.
His face flushed red, rage bubbling up. "Don't you dare touch my daughter."
"She's safe… for the moment. But how long that lasts? Well, that's entirely up to you, old man." I leaned closer, whispering directly into his ear, my breath ghosting over his skin.
He lowered his head, shoulders trembling, before reluctantly bowing in submission.
"What… what do you want me to do, girl?" he asked, voice low, eyes shadowed with despair.
I could practically see the calculation in his eyes. He believed, without a doubt, that his daughter was already my hostage, trapped firmly in my grasp.
"I want you to kill every Master still participating in this Holy Grail War, old man. Every last one of them. That includes yourself. The only ones exempt are me… and my brother," I said, my voice turning cold as steel.
He stared at me like I was utterly insane. "Even your father?"
"Even my father," I answered flatly, without the slightest flicker of emotion.
"Now, take Caster back. Work with him. Hunt them all down. Leave no survivors."
With that, I tossed him a small vial containing the antidote for the poison and turned away without sparing him another glance.
He collapsed onto the floor, defeated, clutching the antidote with trembling fingers. He knew he couldn't die yet, not until he'd done everything he could to try to save his daughter.
Unfortunately for him… I needed her dead.
She should never have existed in the first place. Not before his role was fully played out.
And when that day finally comes… that's when father and daughter can be reunited.
In the afterlife.
A cold, merciless laugh echoed from my throat as I stepped out of the mansion, leaving it and Aritoshi's fate behind me.
...
Question: Should I keep updating this story regularly, or should I start a new one instead—like My Sister Lelouch Is a Yandere, or a story where the MC reincarnates as Zeus or Merlin in the Nasuverse?