Prologue part 1: The first thing I saw was that hell...

The air was laden with smoke and ash, the sparkling sound and heat of the flames, and the smell of burning flesh. The image of this hell became his first memory; because all the previous ones had been swallowed by the flames.

"S-Shirou, p-please, help me..."

Forgive me, please, forgive me... The boy thought as he sobbed.

The red-haired boy walked deep into that hell, next to him, could see people crying out for help, and saw people trying to help those who implored. He heard several people begging for his help, but he covered his ears as tears welled up in his eyes. In the back of his mind, he apologized for ignoring them. He could barely stay alive on his own. His lungs ached, the smoke, as well as the ash, did not allow him to breathe well, his legs were burning, and he had walked until his body reached the maximum of its resistance. But still, he kept moving, sensing that he would never move again if he stopped.

The boy kept walking; he did it for as long as he could, but, in the end, his resistance betrayed him. The redhead fell on the rubble and could no longer walk.

Why did all this happen? I can't remember anything from before the fire started. What was that? It looked like black mud, and it destroyed everything in its path, Thought the boy lying on the ground.

Having reached this point, he gave up, and, suddenly, a small structure collapsed in his surroundings, causing part of his body to end up buried under its rubble.

Being on the verge of death, the boy raised his hand to the sky. "Please, someone, whoever... Someone destroys this hell." He lost what little strength he still possessed, and his hand was about to fall, but before this could happen was caught by someone else's hand.

The redhead made one last effort so he could see and hear whoever had held his hand before it fell: It was a man dressed in a completely black suit, and his eyes made him look like he was dead instead of alive. The man had a faded appearance; however, the sparkle of life returned to his eyes as he held the boy's hand. On his gaunt face, bathed in despair, hope shone for a moment, wept when he knew that he had managed to find someone.

The little boy closed his eyes without strength but heard a few things before he passed out:

"I... I must implant him the scabbard. It's the only way to save him..."

A warm feeling inserted inside the boy; this did not belong to him, but it docked quite easily inside him. But it only lasted an instant before it slowly began to fade.

"Eh? why is it not working? Is it because Saber disappeared a long time ago and, without him, the scabbard can't recharge its power?"

The warm feeling that washed over the boy began to disappear.

"I must do something! ¡The crest! Using the magic crest, I can slow down the bleeding speed, and at the same time speed up the speed of the sheath's healing effect, as well as speed up its natural regeneration." Frustration, the boy could hear the frustration in the man's voice. "With my magical energy depleted, this is the only thing I can do. Stay awake; I will save you. I promise! Even if you are the only one I can save from this disaster. I will not fail, not again."

Suddenly, something strange entered the little boy. Whatever it was, it was something foreign and invasive not only was it not there initially, but it was also not compatible with him; therefore, his body began to reject it. Because of this, the redhead's body began to convulse.

It hurts! Stop it! PLEASE STOP IT!

The boy wanted to scream, but he no longer had the strength to raise his voice.

Gradually, the pain he was feeling due to whatever was being forcefully implanted into him began to be calmed by that warm sensation that suddenly began to grow stronger. However, before he could find out more, he passed out.

He opened his eyes, "That dream again..." rising from the dojo floor, the 13-year-old boy wiped the sweat from his forehead and, lifting his shinai, stepped out of the dojo.

The sun hit his eyes hard and had to cover them for a moment, at least, until they got used to outdoor lighting. "I fell asleep again inside the dojo." After crossing the exit of that place, the boy crossed the patio of the house and entered the kitchen.

"What…? W-What happened here?" the kitchen seemed to be what would remain on a battlefield after a great war: plates and cups everywhere, also the smell of burning filled the room, "old man!" The child yelled in frustration.

I knew I shouldn't have stayed up so late training, but I wanted to train a little more... Did not imagine that it would end in this disaster and, even so, I must be thankful that he didn't burn down the whole house in his attempt to cook.

While the redhead began to clean up the mess, the dream persisted in his mind...

…

After passing out in the middle of all that chaos, he woke up in a white room, a hospital room. After the doctors came to the room and checked his condition, they informed him of what had happened. In summary, there was a terrible accident that caused a big fire; and this devastated the entire residential area in which he lived.

Everything was destroyed by the fire, including his memories, the only thing he remembered was his name: Shirou, and even of that, he was not entirely sure. He was the only one who got away unpunished, physically speaking, and when he was about to start worrying about what his future would hold, once again, that man appeared.

The same man in a black suit who saved him; introduced himself as Emiya Kiritsugu, and without even giving him time to respond, offered to adopt him. He was a man with long spiky hair who wore an expression that made him look like he was always tired. Having nothing and no one, Shirou didn't think twice. Also, his new adoptive father revealed something to him that, for some reason, he could easily accept, told him that he was a magus or, more specifically, a user of magecraft.

For two years, Shirou asked his father to teach him magecraft, but Kiritsugu refused. According to Kiritsugu, learning magecraft meant to a magus the same as walking with death, and for him, a boy who had been close to death in the past, not learning magecraft would bring him more happiness.

Besides, it was almost impossible for Shirou to have the necessary attitudes to learn to use the magecraft. However, due to the redhead's insistence, Kiritsugu decided to analyze the number of circuits his adopted son possessed.

Twenty-seven Magic Circuits; he had seven more than the average mage. None of his magic circuits were of the highest quality, but they were decent. Thanks to this, Shirou should be able to learn magecraft, but there was a problem: He had the same origin and element.

The origin is the starting point that defines one's existence and directs a person's actions throughout life. It is a driving force that comes from within the Root that has managed to flow out of this source and take material form. The form it can take on at times is that of a human being, and all humans match their actions to be in harmony with the driving force that originated them from the moment they enter into the world. The origin works more as a guideline, an instinct for how a person should behave, rather than a conscious decision. If a person awakens his origin, he becomes almost completely subjected to it, if it's even possible to stand against it in the first place.

The elements are the basic substances that shape the world and play an important role within magecraft. Depending on the teachings of the different schools of magic, everything that exists can be classified into different sets of elements. The four classical elements (fire, water, earth, and wind) are said to come from the Arche (Arche is a concept from Greek philosophy meaning the beginning of the universe or the first element of all things) in ancient Greece. The Mage's Association adds Void (Ether) and a few other items to make their classification more practical. A magecraft user normally can manipulate at least one element, although there are users who master more than one, and there are even users of compound elements.

And Shirou, to his bad luck, has the same origin and element: Sword; this was probably due to a mixture of events. First, the terrible accident that "burned everything in the child" and, second, the implantation of Saber sheath. Shirou might have had a different origin and element before this, but these two events must have overwritten them, or at least, that's what Kiritsugu deduced.

Because his Origin was at the same time his Elemental Affinity, magecrafts related to the Five Great Elements were difficult for him to perform, and he didn't seem to have talent in the other various areas of the magecraft either, but there was a specific area in that he seemed to stand out. Spells involving the transmutation of materials belonging to this area, specifically, Reinforcement magecraft and Projection magecraft.

Reinforcement was considered to be a very useful type of magecraft, and its goal was to bring something, anything, to its maximum capacity. It is the basis of all spells that enhance the existence of a target by pouring magical energy within it. However, since there is no clear limit to how much can be improved, "almighty" reinforcements are rare to see. It is the same as adding something to an object that is already complete; in the case of committing a mistake, the target will receive it as poison. Success requires a good grasp of the inner structure to fill openings with magical energy. Reinforcing something will produce different effects, such as: increasing the edge of a knife, more nutrition to food, or in the case of a living being, increasing physical strength and durability. As living beings have resistance to the invasion of magical energy, reinforcing someone is very difficult when using this type of magecraft.

Despite being very useful, Reinforcement is considered a not very special type of magecraft.

Gradation Air, more commonly known as Projection, is a practice involving the materialization of objects, following the caster's imagination. This magecraft is considered by most magi to be useless; as there are two problems with using it:

Anything that the caster materializes would be hollow and therefore much more fragile than the original item. And the second problem with this magecraft was that, due to the influence of the World, everything that is projected constantly degrades until it disappears.

The last thing Shirou seemed to be decent at is using the structural grasp; this allows him to analyze and understand the internal structure of everything he touches, something that other magecraft users don't find too important.

Kiritsugu shared his discoveries with his son, and to his surprise, instead of depressing him, the boy seemed to try much harder to master the few magecraft in which he was talented.

Surprisingly, thanks to their neighbor, Fujimura Taiga, they found out that Shirou had a talent for using swords, which for obvious reasons, did not surprise either of them. They realized this after an argument between Shirou and Taiga due to the latter's vague attitude. Taiga decided to settle the argument through a kendo match, which was silly considering Shirou was a boy and Taiga was a master of the sport. Even so, he accepted, and although he lost, he ended up surprising Fuyuki's tiger in a good way, prompting her to start teaching him.

Thus, at the request of his father, the little redhead began to practice with his neighbor, which Taiga accepted without hesitation, although, over time, Shirou himself took it as part of his routine.

Another thing that Shirou started practicing, also under the influence of his neighbor, was archery. All of this happened because Taiga had just started an internship at a Fuyukihigh school, of which she was a former student, and to which she took Shirou to show it and show off in front of the boy. Thanks to this, the little redhead ended up being dragged by the effusive intern through all the clubs. In the end, they ended up at the archery club, and seeing the demonstrations, the boy asked to be allowed to try, and to everyone's surprise, he also showed great talent in the use of the bow. Although, by comparison, his talent with archery was nothing compared to his talent with swordsmanship.

The thirteen-year-old boy finished cleaning up the mess in the kitchen just before a loud voice echoed from within the house. "Shirou! I arrived; is breakfast ready!?" His neighbor yelled as she walked through the door.

"I'm on it; had to clean up the mess Kiritsugu left inside the kitchen."

"Did Kiri try cooking again?" a young woman asked as she entered the kitchen.

Taiga was a young woman with brown eyes and hair short to her shoulders with fair skin and was about one meter sixty-five centimeters. She wore a simple light-yellow dress.

"Unfortunately, he tried," Shirou replied before turning to see his neighbor, "Fuji-nee, should you go dressed like this to your internships? Don't they have uniforms or something?" the boy asked as he served her breakfast.

"Hmn…? Maybe, but they didn't give me anything when I started it, so they probably won't give interns uniforms," she answered before seeing what time it was, "oh, God! The time! I have to go, or I'll be late!"

Taiga sucked the food up like a vacuum cleaner and hurried out of the house. Shirou could hear her open the door and say, "good morning, Kiri! Shirou told me that you left early!"

"That's right, just got back," his father answered in his usual tired tone of voice, "are you going to complete your internship?"

"Yes! I'll be back for dinner! Remember what we talked about yesterday!" Taiga replied before running off.

"Always so energetic..." the magecraft user said with a slight smile.

"Sometimes I think she is too energetic..." the red-haired man who had moved from the kitchen to the door of the house answered him, "you left a big mess in the kitchen..."

The older man made an uncomfortable and somewhat guilty face. "I-I tried to cook something for both of us..."

Shirou sighed wearily but smiled shortly after. "Come on, 'll serve you breakfast."

"Thank you." Kiritsugu entered the house following his adopted son while holding a large package.

Shirou served his foster father's breakfast and took the opportunity to ask him, "Where did you go?"

The magecraft user stopped eating, and his tired expression, as well as the slightly depressed feeling that always seemed to emanate from his being, disappeared. "Shirou, there are some things we need to talk about..."

"What things?"

"I have decided to teach you how to use magecraft," Kiritsugu spoke in a low voice, almost as if he regretted saying those words.

This surprised the little redhead. "What? Seriously!?"

His father nodded.

"Why did you change your mind?" the confused boy asked.

"I've been thinking about it, and yesterday, I finally made the decision." The old magecraft user sighed. "Shirou, do you remember where my last trip went?"

Shirou nodded, "Germany, right?"

"Yes. You see, before adopting you, I married a woman who was a member of another family of magi and, I started a family..." Kiritsugu stopped and made a gesture of wanting to speak several times, but he seemed to lump in his throat until, at last, he said, "m-my wife, Iri, she died on a mission that we were both sent on by her family."

"A mission…?" the confused boy asked.

The magecraft user nodded. "In the World of Magecraft, I was a kind of agent, a freelancer. And, since I was a child, I have always had a dream..."

"A dream, which one?" Shirou asked, looking interested.

Kiritsugu smiled vaguely. "I wanted to become a hero, an ally of justice. And to achieve this, I worked as a kind of mercenary in that world. I did many missions to save hundreds of people; so that they could continue with their lives." Kiritsugu looked down, showing a regretful expression. "But I failed, and the losses were uncountable, including... my wife."

"I am so sorry," Shirou said, apologizing for making him remember such a harsh past.

The older man shook his head. "It was my mistake, and I had to tell you sooner or later. The thing is, I had a daughter, her name is Illya, Illyasviel von Einzbern, she would be something like your older sister."

"My older sister…?"

"After I failed, the Einzberns, her maternal family, refused to give her back to me. I was a specialist in breaking down barriers and breaking into bounded fields. These are the defenses that protect the territory of a magecraft user. However, after that failed mission, I was crippled, in a sense..."

"You couldn't bring her back, could you?"

Kiritsugu shook his head. "After I came to Japan, I got away from the world of magi and ended up in Fuyuki. Here, well, you know the rest of the story."

Shirou nodded with a smile. "You saved me from the fire, and you adopted me."

Kiritsugu didn't reply, just gave a little nod.

"So, if you've told me all of this, it's because it has something to do with your choice to teach me magecraft. It's not like that?"

"Yes. Shirou, you have twenty-seven magic circuits, seven more than the average mage. Magic circuits are the resource through which we use magecraft. The higher the number and quality of these, the more capacity you will have as a magecraft user. The quality and quantity of your magic circuits are something that is decided from birth; in your case, you have twenty-seven circuits of acceptable quality."

Shirou gave him a small smile. "Yes, I remember."

"Fine. Due to your origin and elemental alignment, it's a waste of time for you to try to learn elemental spells, and so far, you've only shown talent with two spells: Projection andReinforcement. Also, if we're lucky, there's a third that might you can use."

"Three?"

Kiritsugu nodded. "There is a third type of magecraft, but it's too dangerous and complicated to learn right now. I don't even know if you'll be able to use it in the future."

"I understand."

His foster father closed his eyes for a moment before continuing, "Shirou, there is something I need to ask you. In exchange for teaching you to use the magecraft, I want you to help me rescue Illya."

"Rescue my sister? Sure, but will I be able to do it?" the boy asked uncertainty, "we would have to go through the barriers and all that, right?"

Kiritsugu nodded. "That's right, but with the proper training, the materials, and, although we will take a few years, we should be able to get it. Will you help me, Shirou?"

At that moment, and for an instant, the redhead remembered the look full of happiness and hope that his father had when he saved him from that hell, and he wondered.

Will I be able to feel the same if I save someone else? If I save my sister, Illya, will I be able to feel that same happiness?

Shirou didn't understand it, but he knew that he had to live with all his might; for those who did not survive, with this in mind, he replied, "I'll help you. I will do what I can to save Illya-nee-san."

Kiritsugu managed a slight smile. "Thank you." Realizing he had forgotten something, the former freelancer turned to the package he had brought with him, "I almost forgot I got something for you."

"What is it?"

"Open it, and you will know." Kiritsugu handed him a package, which was long and wrapped in bandages with some writing on it.

The redhead took it and, when he put his hands on it, he realized that there was something special about this package.

He quickly unwrapped the package and what he found after removing the bandages of it was: "This is... A katana...?"

"Yes, it's a katana." His father nodded. "When I realized that you had twenty-seven magic circuits, I wondered if, by any chance, you came from a family with an affinity for magecraft. So, I searched the archives for anything that could have been recovered from the fire. But I didn't find anything specific, at least, until I saw you practice with Taiga.

That's when I started looking for anything that could be related to swords, but unfortunately, I didn't find anything either."

"T-then?" Shirou asked enthusiastically. He hadn't even pulled out the beautiful katana with the black scabbard and scarlet red hilt yet and, his body, more specifically, his magic circuits, seemed to be reacting to it.

"I decided to go to the warehouse by myself, and there I discovered it. It was inside a black chest. At first glance, it didn't seem strange at all, but when I opened it and tried to take it, the scriptures were activated. These launched a kind of hypnosis, probably why it remained hidden. But I was prepared and managed to avoid them. Thanks to old Fujimura's contacts, I was able to get it delivered."

"I see…" Shirou seemed mesmerized by the sword.

"And good? Unsheathe it, come on."

Shirou just nodded and took out the beautiful wavy patterned blade. "It has a kanji engraved."

"What does it say?" Kiritsugu asked, also fascinated by the blade.

"Muramasa."

"Muramasa? Is it the last name of a family of magi? I think I've heard it before..." Kiritsugu looked up and tried to focus and remember.

¡PUMP!

"What...?" after hearing the blow, the former freelancer quickly looked down to see his adopted son passed out; he was lying on the floor.

"Shirou? Shirou!?"

The boy began to sweat, and his breathing became irregular. His temperature rose to the point where he seemed to have a fever, and even so, he was still holding onto the katana as if his life depended on it.

"Shirou resist!" Kiritsugu yelled, trying to help his son. But his voice could not reach him. Bright and forgotten flashes began to resurface from those memories that the hell of

Fuyuki had burned. In the boy's mind, only one word echoed loudly: Muramasa.