Kariya Matou's torture started a year ago, on the day that the child of the woman he loved, Sakura Tohsaka, was adopted by the very household he had distanced himself from oh so long ago.
In an effort to save Sakura from the cruel fate of becoming Zouken's heir, Kariya had made a deal with his father, promising that he would win the Holy Grail War in exchange for Sakura's freedom.
Unfortunately for him, that was easier said than done.
Since he had distanced himself from the pursuit of magic for so long, he lacked the power to actually become a Servant's master, and if he were to participate in the Fourth Holy Grail War, he would need to meet the threshold for participation in a single year.
Kariya made a rather extreme decision.
In order to participate in the Fourth Holy Grail War- in order to save the daughter of Aoi from his father, Kariya implanted Zouken's disgusting Crest Worms into his body, forcefully expanding his magic circuits and increasing his magical potential in exchange for the worms eating away at his life.
The implantation process hadn't been easy.
He had to sit in a pit of vile insects for weeks, letting them use him as a breeding ground while enduring the excruciating pain of having those worms violate his body.
They ate away at his mind, at his body and flesh, yet Kariya endured, hoping with the single strand of consciousness he had left that all this torture, this suffering, would allow him to have a fighting chance.
Unfortunately for him, however, it seemed that genetic modification couldn't fully cover up his incompetence.
Despite the year of torture he had endured, Kariya was still far from the other masters in terms of strength, despite also being chosen by the grail.
Thus, Kariya, listening to his father's advice, inserted two additional lines to the summoning incantation to give his servant the necessary power to win in exchange for their sanity.
Because of this, Kariya thought that the servant he would summon would be nothing more than a blood thirsty beast, a monster without a single thread of rationality...
And so,
He was caught off guard by the servant who had answered his summons.
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"Huh...?"
Kariya looked up with his remaining good eye, his expression clouded with confusion.
He was utterly disoriented from the drain of summoning a servant, and thus, he could barely process anything that was happening around him.
Still, though, Kariya knew one thing-
He was no longer in the basement of the Matou estate.
In place of the disgusting walls and ceiling of Zoukens' breeding pit was an endless expanse of beautiful night- a vast tapestry of stars embedded in a blanket of darkness, eliciting wonder in his subdued mind.
Unfortunately, however, in response to his sudden surge of emotion, the Crest Worms inside his body began to squirm uncontrollably, causing pain to shoot throughout his body.
It hurt terribly, but Kariya was used to it at this point.
Ignoring the vile sensation of the worms burrowing into his flesh, Kariya chuckled and really took in the wondrous sight before him, imprinting the image into what was left of his memory.
'... I really wish I could show this to Sakura...'
Subconsciously, Kariya's thoughts drifted toward the young girl whose safety had become his purpose, but a voice cut through his brief moment of thinking.
"Quite beautiful, isn't it? The star's I mean."
Startled, Kariya suddenly whipped around, meeting the gaze of a young man with eyes the color of starlight.
The young man was clad in slender armor covered by a white and red cloak, his exposed mess of hair being a pale blonde hue.
He looked like the very image of a knight.
Kariya was immediately put on guard, but the man simply smiled.
"No need to be so alert. I just wanted to have a conversation with you away from prying eyes."
Hearing his words, Kariya couldn't help but frown as he looked around, realizing that his father wasn't there anymore.
Seeing his expression, the man couldn't help but chuckle.
"Truthfully, I thought you would've noticed the absence of that vile man a bit sooner, but alas, I guess those disgusting creatures in your body are to blame for your dulled senses."
Kariya's eyes narrowed as he stared at the man, his brow furrowing with slight wariness.
"Where am I and who are you? Why did you bring me here?"
The man shrugged.
"The area that we're in is a bit complicated to explain, but you can think of it as my personal space. As for why I brought you here, I'm pretty sure I just said it was to have a private conversation with you, no? And my identity... Well, that can be deduced quite easily."
Kariya gave the man a confused look, not knowing what he meant.
The man sighed.
"What was the last thing you were doing?"
Kariya thought for a moment before widening his eyes.
"Don't tell me- Are you my servant???"
The man smiled humerously.
"Indeed. Though I thought my attire would be a dead giveaway."
He gestured at his knightly garbs and chuckled softly.
The man's humor was lost on Kariya, who was instead wondering why his berserker had enough brain cells to mock him.
Kariya frowned again, his expression slowly filling with horror.
"Wait...! Don't tell me that the-"
"Don't worry, I still possess the madness enhancement trait... It's just that my madness only manifests during specific situations."
Kariya visibly relaxed upon learning this fact, but he still didn't quite look completely at ease.
"So then... What exactly did you want to talk about?"
The man shrugged.
"Well, I just need you to answer a few questions if that's all right."
"Why?"
The man's star colored eyes stared into his comparatively dark ones.
"To determine whether or not you are worthy of being my master, of course~"
His words caused Kariya to freeze for a brief moment, but he soon nodded in compliance.
Immediately upon securing Kariya's cooperation, the man's eyes began to glow faintly as he waved his hand, conjuring a set of glowing chairs.
The man sat down gracefully and gestured for Kariya to do the same, something that Kariya was quite grateful for.
Plopping his half-paralyzed body down onto the seat, Kariya met the eyes of the man before him, and in return, the man offered him a faint smile.
"Alright then, now that we're nice and settled, let's begin the questioning."
The man raised a finger.
"First, I'd like to know your name, date of birth, a few hobbies, and some things you dislike."
Kariya blinked in confusion, but answered quickly nonetheless.
"I'm Kariya Matou. I was born on March 22nd, 1962, and I like photography and traveling..."
"As for dislikes... I guess I'm not a fan of extravagant things."
The man nodded thoughtfully and continued, raising a second finger.
"Next, I need to know the names of every single family member you can think of."
This further confused Kariya, but he still answered obediently.
"My father's name is Zouken Matou, and I never met my mother. I have a single older brother named Byakuya, and though I haven't personally met my sister-in-law, I know they had a child named Shinji. Other than that... I have an adopted niece named Sakura."
Nodding once again, the man asked a follow-up question.
"Any notable friends or lovers you can think of?"
The question made Kariya a little uncomfortable, but he answered after a beat of silence.
"I have a few friends at my workplace, but I wouldn't consider myself to be that close with them. As for lovers... Can't say I've had any."
The man let out a thoughtful hum and raised another finger.
"Mm~ interpret this next question however you want... but how would you react if I were to slaughter every person you just mentioned?"
Kariya fell silent.
"How would you feel if I chopped them up into little bits and fed them to you before slicing open your stomach and pissing on the barely digested chunks of their corpses in front of you?"
The man uttered those diabolical words with a completely straight face, as if the deeds that he had just spoken of were something that he did on the regular.
He continued.
"Zouken, Byakuya, Shinji, and Sakura-"
At the mention of Sakura's name, the man noticed that Kariya stiffened.
"What would you do if I killed them and hung their heads around your mantlep-"
"S-STOP IT!"
With a strength that defied his current worm-infested ailment, Kariya shot to his feet and grabbed the man's cloak with his functional hand.
Pure rage simmered behind his remaining eye as Kariya screamed in the man's face.
"IF YOU DARE TOUCH A HAIR ON SAKURA'S HEAD, I'LL TEAR YOU LIMB FROM LIMB!!"
The man nodded.
"ok."
Kariya gnashed his teeth and clutched the man's cloak even harder, staring into his indifferent, star colored eyes with nothing but harmful intent.
"OK???? Look, I don't care how strong you are- Heroic spirit or not- If you hurt Sakura, I'll stop at nothing to make sure you're dead!"
The man simply stared back at Kariya before nodding thoughtfully.
"Fair enough."
Kariya felt the anger in his system falter for the briefest moment.
"... Fair enough...?"
The man nodded once more.
"Indeed. That response was satisfactory."
Kariya stared at the man blankly.
"Satisfactory??? What exactly are you gaining by asking these questions??!"
The man just smirked at him and gently pushed Kariya back into his seat, not bothering to offer a response.
Kariya's expression darkened.
'Is it still too late for me to request a different servant?'
Letting out a forceful exhalation, Kariya glared at the man in front of him.
"Is there anything else you'd like to ask, or are we done?"
The man chuckled softly.
"Yes, I do actually have another question."
Kariya raised an eyebrow.
"That being?"
The man raised a fourth finger, and with the most serious expression he had put on since meeting Kariya, he asked his final question.
"Why do you seek the grail?"
Kariya was caught slightly off guard by his sudden shift in mood, but still motioned to answer.
Before he could, though, the man spoke again.
"I want the truth. The naked and complete truth behind your participation in this war. If you give me a halfhearted answer or one that goes against my values, I will commit suicide and ensure that your wish is not fulfilled."
Kariya widened his eyes slightly as he met the man's unfaltering gaze.
Instinctively, he knew that this servant wasn't joking- he really would kill himself if Kariya's answer failed to satisfy him.
Still, though, Kariya chose to believe in the cause that he had adopted.
"I... I want to save someone."
The man raised an eyebrow, waiting for Kariya to continue.
"The daughter of the woman I love... I have to win the grail to save her from my father."
The man stared at Kariya with an expressionless face.
"You don't want to win the grail for the woman you love, but for the daughter of said woman? From what you've said, I assume that the object of your affections is promised to another, is she not?"
Kariya nodded with a slightly bitter expression.
The man gestured at Kariya's body, at the tunnels that the Crest worms had torn through his flesh.
"Then... You would house those vile creatures and participate in this war to save the daughter of a woman whose affections are wasted on another? Is that truly your reason?"
Kariya chuckled softly.
"Yes, that is my reason. Is that a problem?"
The man offered Kariya a smile as he rose to his feet.
"Not at all, my master. I actually find us to be of similar mind."
The man knelt in front of Kariya, lowering his head in a pose that embodied the very image of a knight.
Clearing his throat, the man- no, the knight- in front of Kariya summoned a glowing platinum sword and offered it to him with both hands.
Kariya blinked, stunned by the sudden turn of events.
But,
After a moment, he recognized the stance the man had taken and realized what he was doing.
Kariya slowly motioned towards the blade being offered to him and grasped it gently.
As soon as the weight of the blade left the knight's hands, he closed his hand into a fist and touched it to the ground, offering his shoulders in a gesture that had been immortalized throughout history.
After a brief but heavy moment, the knight lifted his head and locked eyes with Kariya.
"Throughout my life, I have only sworn allegiance twice.
The first oath of loyalty I had taken was for Heaven, the celestial body that governs the world.
The second was for Humanity, for the species that had become my source of strength.
Now, I shall speak my oath for the third time— in recognition of the man bearing the resolve to save a life."
Five glittering pearls of light rose from the knight's back and began to circle the two, surrounding Kariya and the kneeling figure in a halo of platinum light.
"I will be without fear in the face of my enemies.
I will be brave and upright, upholding the principles of Heaven.
I shall speak the truth and be true to my ideals, even if it leads to death.
I will protect the helpless and show honor in the face of disgrace."
The knight's eyes began to burn with incandescent light.
"I will become the sword that clears your path.
I will become the shield that protects your cause.
And until the grail is resting in your hands—
I, Arthur Pendragon, hereby swear to serve you as my lord."
The knight, Arthur, straightened his back and brought the fist pressed up against the ground to his chest.
"Do you, Kariya Matou, acknowledge my resolve?"
Kariya nodded quietly, his expression tinged with disbelief as he watched Arthur lower his head once more, offering his shoulders to him.
With a trembling hand, Kariya gently touched each of Arthur's armor-clad shoulders with the glowing blade in his grasp, sealing the pact of knighthood that had just been made.
Arthur raised his head once more and smiled as he met Kariya's eyes.
"May the Stars bless this glorious covenant, and may Heaven look down upon us favorably."