Shinji Matou At Your Service

Magic is a phenomenon that transcends common sense. It involves taking actions that can be accomplished within the realm of common sense but making them happen extraordinarily and unconventionally. This is a collective term for acts that recreate miracles through human intervention. The term "mystery" refers to phenomena that defy common sense. If we remove the constraints of time and money, these phenomena can be reproduced using modern technology.

Therefore, magicraft does not encompass "things that humans cannot achieve." The ability to accomplish such things is referred to as "magic".
During the early stages of human civilization, all magic was 'magic'. However, with the advancement of science and technology, the number of things humans "can do" has increased, and correspondingly, the realm of magic has diminished. In modern times, the quantity of remaining "magic" is extremely scarce, reduced to just a handful. Two known magic with confirmed names are the Second Magic, "Parallel World Interference," and the Third Magic, the "Heaven's Feel: Cup of Heaven," which essentially involves the "materialization of souls."

The use of magecraft requires a magic circuit, an organ that transforms life force into magical energy. It is akin to the internal organs or nerves, and without it, magecraft cannot be utilized.

Individuals who possess magic circuits and can practice magecraft are referred to as magi. Even ordinary people have magic circuits and can learn magecraft; however, their circuits are usually scarce in number, making it quite difficult.

Magi primarily inherit their magecraft and research through a system of familial lineage, known as a "Magus Family."

The inheritance within a Magus Family is not solely limited to bloodline but goes deeper into the concept of "Magic Crests."
A Magic Crest is a mysterious and solidified representation of the magus' lifelong training and achievements. It can be considered a magical legacy that allows a Magus Family to exist as such. Even if the biological bloodline is severed, as long as the Magic Crest is inherited by someone else's physical body, the continuity of that Magus Family is maintained. Even if there are descendants who possess magic circuits, if they lose the Magic Crest, the family lineage is effectively severed in terms of magecraft.

However, magi typically choose successors with exceptional aptitude from within their bloodline, continuously inheriting the Magic Crest. Only when faced with the situation of having no direct descendants or insufficient descendants to inherit the Magic Crest are alternative methods employed to select a successor, known as the heir to family lineage.

The Matou family, to which Shinji Matou belongs, is one such lineage.

Originally, the Matou family was a European lineage of magi with the surname "Makiri." Two hundred years ago, they migrated to Fuyuki City in Japan and changed their surname to Matou, a Japanese phonetic alteration. Starting with the generation of Zouken Matou, the descendants of Makiri gradually began to lose their magic circuits, and by the time of Shinji Matou, they had reached a state of complete decline. To ensure the continuation of the Matou family as a lineage of magi, Zouken Matou chose to adopt Sakura Tohsaka, the talented second daughter of the Tohsaka family, who also belonged to a lineage of magi. Sakura was then renamed Sakura Matou.

However, Sakura's attribute as a magus—how well her abilities as a magus align with a particular type of magecraft—belongs to the imaginary element "Void" and does not harmonize with the Matou family's "Water" attribute. Therefore, from the very first day when Sakura was adopted into the Matou family at the age of five, Zouken Matou forcibly began to modify Sakura's body. The modification method involved implanting a large number of Crest Worms into Sakura's body. These worms were countless insects created and controlled by Zouken.

It was a hellish pain, far beyond what a five-year-old girl could endure.

What is even more terrifying is that the so-called inheritance of the crest is nothing but a facade. In pursuit of his ambition, Zouken added even more abominable things that should be condemned by humanity. Once the modification began, Sakura's yet-to-begin life was cast under a massive shadow, and she became a puppet of Zouken. Although she did qualify to inherit the Magic Crest, she lost the basic dignity of being human.

To prevent this thing from happening, Shinji Matou interrupted Zouken's ritual and declared his intent to kill him.
The body was split in half by a scythe, and the stench of blood, tinged with a hint of decay, was splattered everywhere. However, there was no sign of pain on Zang Yan's face.
"What a beautiful strike, Shinji—let's call you that for now. At least the body belongs to Shinji, and you must have used some method to manipulate it," said Zouken.

"Is it so? As a great magus, can't you even tell if I've been manipulated or not? I am the grandfather who turned into a bug; you can call me Bug Lord." Shinji replied sarcastically.

While Shinji spoke, he used the scythe to separate Zouken's body and then used the petrifying Mystic eye to turn the shattered pieces into stones, leaving only the head.
Zouken carefully examined Shinji and found no traces of magic on his body. "It's not possession, then... Could someone occupy your body directly? No, it's impossible. If that were the case, how could you maintain Shinji's appearance? Have you found a way to break the memory constraints?" he wondered aloud.

Physical information can be falsified but the soul cannot. Otherwise, Zouken would not have maintained the appearance of a withered old man for many years, due to memory constraints. Now that someone has broken through these limitations, it is no wonder that Zouken is excited.

"Who knows?" Shinji shrugged and swung the scythe down. "I went to sleep and woke up like this."
Shinji's words held no falsehood.

As Zouken said, the soul within his body was not the original Shinji Matou. The original Shinji Matou was an ordinary boy without any magical talent, with the mind of an average six-year-old. He had no abilities, let alone the idea of killing Zouken. The one with the ability to plan and carry out the murder of Zouken, now inhabiting Shinji's body, is the soul of an adult.

As for how he occupied Shinji's body and what happened to the original soul, the newly born "Shinji" did not know. His original body was not Japanese, European, or from this world. He woke up from sleep only to find himself in a different body with a different identity, and even the world had changed.

Through an analysis of residual memories in his brain, he quickly determined the situation. Though unbelievable and often doubting if he was dreaming, he had indeed arrived in a familiar yet different world through the legendary method known as "Isekaid."

It was a fantastical world, once thought to be virtual, created by Type-Moon and Nasu.

It was a brilliant world with various wonders, countless branches, and timelines.

Here, there might be the Fate series, Tsukihime, Mahou Tsukai no Yoru, Kara no Kyoukai. It was a world for which countless fans of the two-dimensional realm yearned.
Now he finds himself here, unfolding his own story under the identity of Shinji Matou.