Kiritsugu looked at Shirou, who, for the first time since being adopted, showed emotion. He appeared annoyed and ran away from the teenage girl, Taiga, whom they had just met as they were moving into their new home.

Taiga watched him run and commented, "Shirou is a bit weird."

Kiritsugu nodded. "Well, he did survive the fire. He remembers the burning, but nothing else."

Taiga nodded thoughtfully. "Why not take him to a psychologist? I hear they can fix the brain—or so they say."

Kiritsugu hummed. "That might be a good idea."

After dinner

Shirou looked at Kiritsugu. "Old man, can you teach me Magecraft?"

Kiritsugu sighed. "No."

Two weeks later, The psychologist addressed Kiritsugu. "Sir, I think the fire left too deep of an impact. What he needs is a purpose."

Kiritsugu nodded. "A purpose, huh."

That evening

Kiritsugu looked at Taiga after finishing their English lesson.

Taiga smiled. "All done!"

Kiritsugu nodded. "Taiga, this isn't really on our topic, but can you think of this as a game and try answering a few of my questions? You know, just like how you give advice to your juniors and friends."

Taiga grinned. "Oh, are you trying to test my debating skills? Ayyyy, fine! Come at me!"

Kiritsugu nodded. "Alright. Let's say there's a boy who comes to you, asking you to teach him Kendo. Not because he loves Kendo or extracurricular activities, but because he wants to get stronger. His only motivation is strength. What would you do?"

Taiga tilted her head. "Hmmm… That's not so rare. Plenty of freshmen join the club with those kinds of motives. But—"

"There's a twist," Kiritsugu interrupted. "At home, he has a real katana within his reach. His family is careless, and he can take it out anytime. If you teach him Kendo carelessly, he might use that katana and hurt someone one day. So, what would you do?"

Taiga furrowed her brow, her playful tone giving way to seriousness. "So, locking up the katana or throwing it away isn't an option here, huh? You're just testing how I'd handle it as a senior Kendo club member, right?"

Kiritsugu nodded. "Exactly."

Taiga straightened, a mischievous glint returning to her eyes. "Alright! I'd teach him Kendo. Even if I reject him, he might just pursue online lessons or resort to even worse methods. So, I'll teach him Kendo—but only the swings. No footwork, no sparring, nothing but swinging. I'd make him do ten sets of a hundred swings every day, rain or shine, morning and night, without fail."

Kiritsugu raised an eyebrow. "Is that… even Kendo?"

Taiga grinned. "Nope. I'd just teach him some nonsensical essence of Kendo. PAM PAM! I'd focus only on his shoulders and tell him to imagine swinging toward a grandma's shoulder, massaging her. I'd also teach him the worst way to handle a shinai so it'd fall off every time, even when he swings seriously."

Kiritsugu nodded. "Ah, I see what you did there."

Taiga nodded. "If he practices so much nonsense, with no joy and only misery, plus zero signs of getting stronger, he'd definitely give up—as long as he's not a massive idiot. He'd probably say something like, 'Kendo is useless.' That would help him realize that a sword will never bring him any good, and case closed. But if he starts thinking, 'If a sword can't do it, then I'll go for guns,' and goes astray, that'd be outside the concern of a Kendo practitioner. Then, I'd have to look at the case from the perspective of Fuyuki's justice—but that'd beat the purpose of this question, wouldn't it?"

Kiritsugu chuckled. "True. To be honest, that was a really unexpected answer… So you'd 'deceive' him, huh?"

"Well, it's only fair," Taiga shot back. "The kid's motive is fraudulent, after all. He doesn't want to be a swordsman; he just wants strength. My approach would help him realize his mistake in the most sincere way possible."

Kiritsugu's expression darkened slightly. "And what if he believed every word you said? What if you didn't want to betray his trust?"

Taiga's grin softened. "Even if it hurts, I'd still guide him down that 'wrong' path. Sometimes, the only way to correct misconceptions is to let someone walk the road themselves. It's harsh, but it's the fastest way to clarity. Besides, lectures and nagging rarely change anyone's heart."

"And all the effort he put into that 'nonsense' Kendo… it'd just be wasted time?"

"That's fine," Taiga said with a shrug. "Time wasted is what youth is for. Call it a tuition fee for life lessons."

Kiritsugu's eyes narrowed. "But what if he never realizes it's nonsense? What if he follows that path to the end?"

Taiga's smile widened. "Then that'd be a very amazing thing to witness. So, I'd praise him. If he invests his time and passion into something and sees it through, then it's no longer nonsense but a whole new path. The boy has mastered a swinging technique that tests one's undying will."

Kiritsugu leaned back, slightly impressed. "And you think such a person wouldn't harm others?"

"Of course!" Taiga laughed. "If he becomes such a figure, he wouldn't have room in his heart for ill will. I'm pretty sure he wouldn't harbor any ill feelings toward the master who taught him such 'nonsense.' Everything would work out in the end!"

Kiritsugu smiled faintly. "You're amazing, Taiga-chan. Really something else."

"Heheheheh, stop it! You're gonna make me blush!" Taiga puffed up her chest. "If you keep flattering me, I might just end up getting a teaching license! What would you do then, huh?"

Kiritsugu shook his head, a small chuckle escaping his lips.

A few minutes later

Shirou looked at his father. "What is it, old man?"

Kiritsugu hummed. "Shirou, once Taiga returns home, can you come to the dojo for a while? I'll start your lesson in Magecraft."

Shirou's eyes widened. "Eh? O-okay."

At night

Under the starry sky, Shirou sat on the dojo floor. "Hey, old man, are you really going to teach me some Magecraft?"

Kiritsugu nodded. "Yep. Shirou, I'll only teach you what's within my capabilities. But the content might not be what you expect. You might be disappointed. If you get tired of it, don't hesitate to stop, okay? I know I've said this many times, but this exercise is truly unnecessary."

Shirou smiled. "It's fine! I just wanted to be able to do what you can do, old man."

Kiritsugu hummed. "Listen, Shirou. To learn Magecraft is to depart from common sense. We die when the time comes. We kill when we have to. That is our true nature. We don't live by the living; we live by death. Magecraft is something that destroys oneself from the inside. There's no other way around it. What I'm going to teach you will stir more conflicts than not. So… never use it in front of others, and it's also quite difficult. Take the practice seriously."

Shirou nodded.

Kiritsugu looked at him intently. "The most important part of Magecraft is that you must never use it for your own sake. Use it only for others' sake, but always in secret. Tell no one. With that, Shirou, you may be able to use Magecraft, but you will never become a magus."

Shirou blinked. "I see. It sounds complicated, but I think I understand now. I never wanted to be a magus. I just wanted to learn Magecraft from you, old man. So I'm fine! I'll listen to what you said."

Kiritsugu nodded. "Good. Let us start with the basics. First, project an image of your entire body—from your organs to your fingers, to every single nail, even to every strand of your hair—and manipulate them. You must learn to maintain that level of focus and concentration first."

Shirou blinked. "The first step sounds rather hard, old man."

Kiritsugu nodded. "Of course. You have to rework your body into the equipment to use Magecraft. Then, think of a word that will trigger your maximum concentration. Just like pushing a button, you need one word to flip your consciousness around. A strong word."

Shirou scratched his head. "Is that something like… a magic spell?"

Kiritsugu gave a small nod. "Not far off. It's a spell meant only for you—a word that has a deep meaning and resonates in your heart."

Shirou frowned, trying to find the right word. "Hmm… I see… but it still hasn't come to me."

"You don't need to rush," Kiritsugu said. "It's just a word that should be persuasive to you, and you alone."

Shirou murmured to himself, trying to grasp the idea. "Just like pushing a button… just like flipping a switch."

"Yep," Kiritsugu affirmed. "Take your time. No need to rush."

Shirou nodded slowly. "Understood."

Kiritsugu added, "Also, you'll work hard in a gym, attend Kendo lessons with Taiga, martial arts classes, and Kenjutsu lessons—all to improve your physical ability."

Shirou looked at his father. "Old man, why do I have to train so much?"

Kiritsugu hummed. "Shirou, you need to possess a superhuman-trained body to handle the strain of repeatedly casting spells and to be prepared for superhuman close combat in future situations where you might run out of Od. It's very important."

Shirou nodded. "Okay. Do we have any books for it?"

Kiritsugu looked at him "We'll see how much you can learn before we get the books"

Four months later

Shirou stood in his room, staring at his hands. He had made progress—he could now turn his nerves into circuits, but maintaining the transformation for longer periods still proved difficult. As he stood there, he heard the door slide open and turned to see his father entering.

Kiritsugu looked at him, concern in his eyes "Shirou, why aren't you in bed?" he asked.

Shirou hesitated for a moment before answering, his voice soft. "I had a bad dream."

Kiritsugu nodded, his expression softening. "You can sleep with me tonight," he offered gently.

Thirty minutes later, Shirou lay wide awake, staring with open eyes as his father slept soundly beside him. Shirou had an idea as he bit into his pillow to stifle any noise and, with a determined look, began turning one of his nerves into a Magic circuit, pushing through all the pain. Once it was done, he carefully reached over and touched his father's back.

Shirou took a deep breath and activated his Structural Grasping. His focus sharpened as he felt his way through Kiritsugu's physical Magic circuits—his Magic Crest—carved into his father's back that connected to something immaterial through the Brain as he let it go. Shirou analyzed them, repeating the process in his mind over and over again until his nerve circuit finally stopped functioning.

He nodded, a small realization dawning on him. "So, I can turn other body parts into Magic circuits, not just nerves..." he murmured, contemplating the new discovery. However, being a newcomer to Magecraft, Shirou couldn't know that the Magic Crest were sets of circuits passed down from a predecessor, carved into a Magus to pass on a Magecraft's spells and knowledge to the next generation.

Two years later

Kiritsugu walked down the hallway, feeling slightly anxious. Tomorrow, he would be traveling to Germany to try and retrieve his daughter, Illya. He paused, a thought suddenly occurring to him.

Making his way to his son's room, he quietly opened the door and found Shirou asleep. Kiritsugu approached his son, then, with a deep breath, activated his circuits. The familiar pain surged through him as the curse of Angra Mainyu twisted its hold—his body and circuits were slowly deteriorating under its weight.

He placed his hand gently on Shirou's chest, and as he did, a golden ripple formed, Gold energy flowed outwards, and soon a sheath had formed. Kiritsugu pressed it to his chest, watching as a golden ripple formed, and the sheath sank into him. and though the sheath was inert, he hoped it would offer some help, however small, in the days to come.

Two years later

Eleven-years-old Shirou Emiya looked around his small workshop. Near the end of the room was a small bookshelf containing Nine tomes, each dedicated to the Magecraft he knew.

One spell was Reinforcement, the art of using magic to strengthen an existence to their utmost limit—such as reinforcing a knife's sharpness or enhancing nourishments of the foods. There were Four tomes on this: one focused on reinforcing normal objects, another on reinforcing Magical objects-(Mystic Code's), Another on reinforcing the caster's own Body and another on reinforcing other being's. The bookshelf also contained One tome on the spell "Modify"(reinforcement based Alteration) The art of using magical energy and Structural Analysis to change its structure.

The bookshelf also contained three tomes on Alteration, the art of changing or adding properties to or of the objects. A master of Alteration can make drastic changesto substances, such as turning metal into rubber, fire into ice, or concrete into mud.

The next tome was dedicated to Projection, the art of materializing objects in accordance with the caster's imagination through the use of magical energy.

The final tome focused on utilizing Mana from the air, teaching how to convert it through his Magic Circuits, alongside the conversion of Od generated from his soul, to fuel his spells.

Shirou slowly rose from the floor, his muscles slightly tight from sitting still for so long. He stretched and brushed off the dust from his pants, Shirou could not shake the sadness that lingered ever since his father's death two months ago. After the loss, he had thrown himself into training—particularly Magecraft—but despite his dedication, he felt no progress. In his grief, he had devised a dangerous plan to push himself beyond his limits.

[P.S In this Au Kiritsugu died a year early due to his attempts to break into Einzbern Castel and using his Magic crest which hampered his body more]

On his desk lay a photo of himself, his father, and Taiga at a theme park. He stared at it, his resolve hardening. No matter the cost, he had to make progress.

"Gahh—AHHHH!" Shirou howled in pain as a sensation like a hot knife being etched into his mind overwhelmed him. He powered through it, enduring as the changes took hold, the process agonizingly slow. Twenty minutes later, the transformation was complete, but the connection was beginning to fade. Desperate, he used all of the circuits—including the one he was currently altering—and cast Reinforcement to stabilize the circuits, reinforcing their existence from the inside out.

"AAAAAAAAARRRRRRRRGGGGGH!" Shirou screamed as his brain felt like it was being split apart, as though molten lava was coursing through his nerves and his body was set aflame. It felt as though thousands of needles were piercing him from every angle.

A while later, the pain finally subsided. Shirou felt something "click" within him as his temporary nerve circuits faded. He collapsed onto the floor, exhausted, but forced himself to focus. Slowly, he attempted to use Magecraft, and to his amazement, the experimental connections had activated. As he analyzed himself, he realized that he now had a single magic circuit, With any sound, he ended the spell, dragged his weary body to his room, and collapsed into bed.

After Two days, Shirou touched his body and analyzed it. To his happiness, that one circuit hadn't disappeared; it had remained stable. A smile tugged at his lips. He had done it. "Dad, I did it... I hope you're watching."

Two years later

Shirou opened the suitcase he had found beneath his father's bed. As he lifted the lid, he discovered a golden and blue sheath.

"Huh, a sheath... What does it do?" he muttered to himself. He activated Analysis on it, and a sharp headache immediately shot through his mind. But then, the information became clear—this was Avalon. He didn't know how or who had used it, but the knowledge settled in his mind.

A few minutes later, Shirou let out a quiet moan. "Huh... interesting," he murmured, intrigued by the sheath's significance. He pressed it against his chest, feeling a strange pull. As soon as he did, a golden ripple formed around him, and the sheath sank into his body, vanishing without a trace.

Shirou stood up and made his way to his workshop. Once there, he began analyzing his body to locate Avalon. After finding it, he focused on the sheath itself and carefully analyzed it. He then projected it, watching the golden-blue sheath materialize in front of him.

Once the projection was complete, he began altering the sheath, trying to make it function to his will. Over and over, he repeated the process—analyzing, projecting, and altering Avalon. Each time, he grew more determined to harness its power for his goals. He resolved to continue this relentless cycle until he could replicate it perfectly, just as he had with other objects he had studied and projected.

It was a long, arduous process, but Shirou pressed on, unwavering in his pursuit to gain mastery over Avalon.

-Two years later

Fifteen-years-Old Shirou walked through the quiet streets of Fuyuki City, the dim glow of streetlights barely illuminating the chilly night. His thoughts wandered to mundane matters as he enjoyed the crisp air, unaware of the fateful encounter that awaited him.

A strange sound caught his attention—an otherworldly hum, almost like a song resonating in the air. Curiosity led him to a secluded alley, where he witnessed a man cloaked in a Suit chanting arcane words as a Corpse near the man's feet on fire.

Shirou froze in fear realizing he had stumbled upon a Magus performing Magecraft. The Magus's eyes snapped to Shirou, cold and calculating as there was no hesitation. as the Magus extended his hand and chanted as an invisible force ripped as Shirou tried to move but in a flash blood flowed and Shirou fell on floor all of his Limbs were now cut apart as blood flowed like a river

The Magus stepped closer "An unfortunate witness," he muttered his voice devoid of remorse.

Shirou looked as he thought [I-I cant die now not to someone like him]

The Magus the raised his hand to use a spell and burn Shirou to Ash but a chilling presence filled the air as a Hand burst through his chest with his heart on a hand

A women with Blonde Hair and Red eye appeared as the figure went Infront of Shirou as alongside her was another Teenage girl with Brown Hair and Red eyes

The Teenager crouched beside the fallen boy "You are still alive"

Shirou looked at her, his mouth full of blood. "Help," he spoke weakly, struggling to stay conscious.

She didn't know why, but she made a decision. "I can save you... though it may end up being more of a curse than a blessing."

The woman blinked in confusion. "Are you trying to convert him?"

The teenager nodded. "I don't know why, but I want to."

Shirou breathed heavily. "Please..."

Without hesitation, the teen bit into his neck, drinking his blood before injecting a large amount of her own into him.

"Well, what do we have here? Another toy for you, sister?" a childish voice spoke from behind them.

The woman, Arcueid, turned sharply to see a 14-year-old looking Teen standing nearby. She snarled. "Why are you here, Altrouge?"

Altrouge smiled mischievously. "I was just passing by when I smelled your detestable stench. I followed it here for a rematch, only to find you making a new toy. How typical, Arcueid."

Arcueid's eyes narrowed in anger. "Satsuki is not mine."

Altrouge hummed thoughtfully. "Yes, yes... you and that blue-haired girl bonded over the death of the same guy. How tragic."

Arcueid growled. "Get out."

Altrouge's gaze flickered to Shirou's wounds, which were starting to heal. With a sly grin, she transformed into her second mode. In the blink of an eye, she grabbed Shirou and bit into his neck, pumping him full of her blood.

"Gahh!" Shirou screamed in agony as it felt like his body was tearing itself apart.

Arcueid acted quickly, striking Altrouge and snatching Shirou away from her grip.

Altrouge smiled wickedly. "This is enough for now, but I wonder... who will the boy follow, I wonder? Will he choose his new 'parent'?"

She hopped onto her dog-squirrel-bunny beast and left, vanishing into the distance.

Satsuki rushed to Shirou, her face full of concern. "Sensei, what will happen now?"

Arcueid frowned deeply. "I don't know. If he survives, he may be compelled to follow Altrouge... so I need to do this."

Without another word, she bit into Shirou's neck and pumped him full of her own blood.

"AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!" Shirou screamed as his body convulsed violently, torn apart by the conflicting transformative power of three different bloods. the three different blood fought inside him, threatening to destroy him completely.

Inside Shirou, Avalon and its numerous copies flared to life, sensing the overwhelming threat. Most of the copies had been formatted to forget its wielder and when inhim they had deemed Shirou to be semi-worthy for them due to his resolve and goals as the Sheath's activated within him to protect it's current holder from death. The original Avalon sensing energy from its copies turned on at full power and it then took all the energy needed from the copies and started flowed 'Healing energy' intoShirou's body. It melded with the powers from the blood of the three Dead Apostles.

As the healing energy merged with the Magical energy of the blood, it started dramatically changing Shirou's body

"Gahh" Shirou convulsed more as the Four energies fought within his body

Just then, a portal opened as a man with white hair, a small beard, red eyes, dressed in a three-piece suit and holding a crystal sword, stepped out.

Arcueid's eyes widened. "Grandpa Zel!"