Magic, a subject of fantasy, boggled Shirou's mind with the sheer number of written works on the topic. However, none of the fantasy works he encountered pertained to the subject of real Magic. It was an unfortunate truth he discovered as he delved into a rabbit hole that somehow led him to princesses and romance stories.
The Japanese system of compulsory education required that children underwent six years of elementary school and three years of lower secondary education, totaling nine years of mandatory education. As a seven-year-old child, Shirou would have been expected to attend an elementary school. However, it was halfway through the school year and Kiritsugu, considering the circumstances decided that it would be best for Shirou to have some time to adapt before registering in a school. This wasn't an issue with Shirou's questionable governmental records.
Hence, Shirou found himself at Fuyuki City library. As a child of his age, particularly in the 21st century, there weren't many activities to occupy his time outside of school. While most other children would indulge in the comforts of the modern age by exploring cartoons, the typical Japanese child did not live in a world where Magic was actually Real.
Although Kiritsugu had initially planned to leave Shirou at home with a sitter while he attended to matters outside, Shirou requested to be dropped off at the library. Apart from the fact that their newly furnished Emiya residence lacked a library, a library was not exactly a staple of the typical Japanese household. Kiritsugu didn't strike Shirou as the scholarly type either.
Since Kiritsugu wasn't going to disclose more about magic in the immediate future, and considering the fresh and slightly awkward father-son relationship, Shirou believed that he could find the answers he sought at the library. Fortunately, the Fuyuki Central Library was untouched by the fire. Aside from a weird incident that mysteriously destroyed the shutters of the library a couple of days before the fire, the library was left intact.
Once his father left him to his own devices, Shirou approached the librarian for guidance on the section of books related to magic. The librarian promptly directed him to the fantasy section within the fictional books.
Upon quickly browsing through a few picture books featuring princesses trapped in towers guarded by dragons, Shirou realised he had been led to the wrong section. These books hadn't even mentioned magic. Nonetheless, finding them mildly entertaining, he persisted and eventually stumbled upon books involving evil wizards and witches cursing princesses. While these well-illustrated books could be described as 'exciting,' they still fell short of Shirou's initial expectations.
The books he had read was not exactly what he was looking for, however, he felt he was on the right track. Perhaps the children's book section didn't hold the answers he sought. His current circumstances reminded him of the challenges posed by his amnesia.
Prior to consulting the library, Shirou knew in the back of his mind that princesses were somehow connected to magic, but his lack of memories prevented him from establishing the necessary links. The knowledge resided within his mind, but the corresponding experiences required for connecting these pieces of knowledge were absent.
Shirou decided that one of his priorities would be to read more books in order to gain those experiences and bridge the gaps in his understanding, for it would help him better adapt to the world.
First and foremost, he needed to learn more about magic, as it represented the most significant gap in his knowledge, considering that he probably had no awareness of its existence beyond fiction prior to the fire.
Ascending to the next level of the library, Shirou ventured into the adult's section, where he faced a few strange looks and inquiries. Eventually after consulting other individuals, he was directed to a section dedicated to mythology and historical legends.
Being a Japanese library and as a credit to it modernity, it housed an equal number of books on Japanese mythology and folktales as well those from the rest of the world, such as Greek mythology and Arthurian Legends.
He would spend the rest of the day and subsequent week immersing himself in these topics alongside grabbing a few dictionaries, considering he was only seven years old. As a child, his language skills couldn't be expected to be exceptional. Especially as he was browsing in the adult section.
Kiritsugu Emiya knew he was not a good man. The weight of his sins burdened his conscience, and he couldn't deny the suffering he had caused to countless individuals, including the child he left at the library early that morning.
Perhaps the way his life had turned out was Karma, his punishment for living the way he did. Yet he was on his way to commit another sin, promising himself it would be his last. It was the same rationale in which he would commit the sin that was the one that led him down this path before. He traded lives for the greater whole. It all began with his first kill, the death of his only family member to prevent a greater tragedy from happening after the one on the island.
Reflecting on his journey, Kiritsugu wondered if he had started in the wrong way. His dream had been noble, to become a Hero of Justice, but perhaps he had been too naïve or not naïve enough. If that incident had never occurred, how different would his life have been? Would his mindset have remained childlike, altering the way he approached life and pursued his dream?
With a disbelieving sigh, Kiritsugu dismissed his own wishful thoughts. Maintaining the mindset he had as a child would have led to his demise, especially in the aspect of the world he lived in. He would either have ended up dead in a ditch or followed his father's path of madness. Justice, he realised, didn't truly exist in this cold and unfeeling world.
In thirty to forty years, Fuyuki City would also experience Justice, but it would be a cruel one. Many lives would be lost. Death was the justice he brought, the method he employed—a calculated exchange of lives.
His plan was to prevent the tragedy that befell his adopted son from happening again, and to so many countless others. To halt the Fuyuki Holy Grail War. The Holy Grail had been corrupted by Angra Mainyu, containing the sins of all humanity, including Kiritsugu's own. Releasing it would be like opening Pandora's box, unleashing Chaos upon the world. This time, not even hope would be left in its wake.
Hence, he was now planting a bomb in a forest ten kilometers away from Mount Enzo, Fuyuki City. The explosives were strategically placed on a mana ley line that would go on to intersect with many others in the city. Once ignited, the blast would disrupt the ley line network around Mount Enzo, rendering the gathering of magical energy in Fuyuki impossible and preventing another Holy Grail War.
These actions would mark the end of his involvement with the Holy Grail War. He recalled a conversation with Irisviel, his late wife, about his plans after the war. The current situation wasn't what either of them would have expected.
Irisviel had given birth to Illya, their daughter, as Kiritsugu's hope for a future beyond the war, a connection to the last remnants of his humanity. Although Illya was far away in Germany, she remained his beacon of hope, and he intended to bring her back eventually.
However, there were other concerns on his mind. He had just resolved one issue by preventing another Holy Grail War. His solution resounded with his lack of trust in Magi. Throughout his life, he had witnessed the lengths they would go to for their goals. That's why he hadn't gone to Germany yet. Illya would be fine for now.
Kiritsugu had a deep understanding of Acht, the head of the Einzbern Family. Despite his cold and uncaring demeanor as a Magus, Acht was not overtly cruel. Unlike Kiritsugu's other opponent in the Holy Grail War, Kirei Kotomine, Acht did not crave suffering.
At his core, Acht was more than just another Einzbern homunculus; he served as a vessel, a terminal for Jubstacheit von Einzbern. Acht was an artificial being, not only in body but also in mind. Though he possessed free will, he was fully fixated on his purpose.
Acht was driven by an obsession left by the last of the true blooded von Einzberns — to seek the third magic and win the Holy Grail War. It was his mission and purpose, which explained why he was comfortable leaving his daughter, Illya, in the Einzbern castle in Germany during the war. Acht understood that mistreating Illya served no purpose; she would be safe, at the very least.
However, Kiritsugu was not yet prepared for the reunion with his daughter. As cold and mechanical as he had made himself throughout his life, he couldn't deny that Illya was the product of love between Irisivel.
He questioned how he would break the news to his daughter about her mother's death, how he would explain his role, and how would he convey that ultimately, her sacrifice in the pursuit of Kiritsugu's goal had been in vain.
Ignoring how his future reunion with his daughter would turn out, there was a reason why he hadn't yet returned to Germany. If kiritsugu was a more naïve man, he might have brought Shirou with him to Germany after the fire, introducing the boy to his sister.
However, Kiritsugu knew better. Regardless of how his daughter might receive him, the question remained whether he would even be welcomed into the confines of the bounded field of the Einzbern castle.
Surely the head of the Einzbern family knew about the events of the Fourth Holy Grail War. While reports were sent to the Mage association by the church after every Grail War, the Einzbern would have also dispatched observers to scrutinize the events of the war.
While the rest of the Clock Tower may have seen the Einzberns as a family of flesh puppets chasing an impossible goal, Kiritsugu knew differently. The Einzbern's were a Magus family, living in a castle that stood above a ley line in Germany's Rhine region, a perfect location for the world's premier Homunculus production facility.
The Einzberns specialized in creating Homunculi of all types, and Magi would frequently contact their Homunculus liaison in England to place orders. Although their finest products were not available for sale, their regular products commanded a considerable sum for the average Magus Family. Even if one couldn't obtain a peak Einzbern model Homunculus, there was no equal across the entire Moonlit world.
This accomplishment was the result of the Einzberns' hard work and cumulative research over a millennium. Even without considering their specialty, they excelled in Alchemy and Golem production, making one of the wealthiest, albeit low-key families in the Moonlit World.
Was it the awareness of the Einzbern's power and influence, or was it Illya's potential reaction that deterred Kiritsugu from returning to Germany? Perhaps those were contributing factors, but his true reason was guilt. He carried guilt for the lives taken throughout his path, guilt towards Illya for what had transpired, and guilt towards Shirou, his adopted son, for inadvertently making him an orphan.
Kiritsugu's presence in Japan served as his penance. It was his way of atoning for his actions and taking responsibility for Shirou, who had lost his family due to him. Since the boy had suffered because of his actions and choices, Kiritsugu felt it was his duty to try and restore what he could of a normal life for Shirou.
His self-flagellation was a form of punishment. Every day he remained unaware of Illya's well-being, every day he missed her he felt the pain of their separation. But Kirisugu believed the emotional pain he felt daily was deserved for his sins towards the world and for walking down the path he had chosen.
The origin of his guilt was difficult to pinpoint. Did it start when he realized his naivety and ignorance regarding his father's actions? Or was it when he ignored Shirley's wishes, ultimately leading to the tragedy that unfolded on that village?
Regardless, Kiritsugu had done little to assuage his guilt since the fire. He had not made much amends or taken much penance for his mistakes. He had been consumed by his emotional upheaval after the events of the Holy Grail War. He had been brooding and reeling from the past, of what he had done, of what he had lost.
It was high time for him to take responsibility and play the role of a father to Shirou, despite his own personal struggles.
Authors notes:
A bit on what Shirou is doing after the fire, rediscovering his life. We see his Origin at work here in his curiosity wanting to get to the root of things.
Kiritsugu POV on his emotional state after the fire. And a bit on the Einzberns. I always thought it was weird that in canon it took a few years before he went to germany. Considering his tendencies for self punishment, I felt that I wrote him pretty well.
Also the Einzbern stuff is kinda my invention but it makes sense. You need materials to make more homunculi after all and those cost money. Magecraft requires an exchange at some level. Especially when you are literally creating a new sentient being. Considering that Illya didn't have any problems living in the Einzbern castle in Fuyuki especially considering how it was destroyed in the Holy Grail War, the Einzbern's must have been loaded.