(a/n: people I found out that all of the cast used to go to different schools during the early years so I made a mistake. I got misled by Ilya verse stuff and assumed that fuyuki being a small city lacks multiple schools so take this as AU. The rest will be the same and they will move on to Clocktower in middle school so the school arc will not be necessary except for catching shinji.)
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Shirou woke up from his dreams with an unexplainable certainty that it was the end of the war.
He sat on the mattress and was lost in thoughts, remembering Kiritsugu`s words about the visions of the Grail War shirou went into the bathroom.
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On the breakfast table, the father and son pair sat in front of each other and ate in silence. Breaking that silence shirou said
"Dad, why did you order sabre to destroy the holy grail, when your wish was in front of you?"
The magus killer paused swallowed his bite and put the chopsticks aside before saying
"I take it as you have watched the whole 4th holy grail war. And shirou the grail is not what it is represented as." after saying this kiritsugu was in deep thoughts
< I don't wish to tell him about what happened but as he has already seen what happened, so I should tell him the truth of the grail as partial information is more lethal than no information.>
Breaking his pause kiritsugu said
"Either the grail was corrupted with something or it was made like that is what I don't know but the grail is not holy, it more aptly should be called demonic."
"Inside the grail, I was shown the vision of how my wish will be materialised."
He then began explaining the simulation in The Grail and how the conclusion came up as killing all humans to stop wars.
He skipped over the part of him being forced to kill his wife and daughter and all the emotional things and stated raw facts before his son.
Hering the reality of the holy grail shirou was enlightened and sat there in silence. kiritsugu said
"Now go to school it's already late."
Looking at shirou leaving the room kiritsugu thought
< I don't wish to live anymore, Iri i will join you soon as soon as I make shirou capable of being by himself and talk to Acht to release Ilya. shirou will take care of her.>
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While walking to school shirou thought of the past month`s activity
Rin and shirou spared twice more and shirou ended up losing both times. He felt he had made improvements in swordsmanship and marksmanship. But his best accomplishment was in magecraft or bounded fields specifically.
Yesterday he was able to cast a bounded field at the last try successfully. Kiritsugu said that he would teach him about sigils and improvements in bounded fields as well as how to breach them.
Soon he reached the school gate and while going to class crossed paths with Issei, who greeted him and said
"Emiya you are finally here, I thought you would be absent like seaweed head."
Hearing the nickname of Shinji shirou laughed and then talked with his friend till they arrived at his classroom.
The class passed on and as the bell rang shirou took his lunch box and went outside the class. He found Issei en route to the roof and invited him to eat but Issei replied
"Emiya you go by yourself, the she-devil is most likely there and I don't wish to meet her."
Nodding his head shirou went to the roof and found no one there. Eating alone he enjoyed the peace and quiet that he recently has come to appreciate after regular meditation.
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Reaching home shirou changed into martial arts robes and started meditating with his shinai.
Taiga came 30 minutes late that day and after greeting each other they warmed up for the practice. The teacher and student pair both took a stance with their shinai in front
The eye contact between the pair continued until shirou took two steps forward and swung the sword in a vertical slash.
Taiga blocked the slash with ease and pushed shirou back. Then she took a step to the side and slashed at Shirou`s left shoulder.
Aligning the blade at an angle shirou deflected the attack and stepped forward from the left side he performed an upward swing, that was elegantly dodged by Taiga with a tilt of her head and a turn of her torso.
With a turned torso she sang her blade inwards hitting on Shirou's jaws and destabilising him despite his guard.
Reestablishing himself while defending shirou took the initiative again by dodging a swing with an instinctive duck.
This back-and-forth went on for 10 minutes until Taiga scored a clean hit on Shirou's head.
So the lesson ended after a few more rounds and for the rest of the night shirou practised magecraft.
Projecting various household blades and trying to project his mystic code shirou fell asleep.
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The next morning after breakfast the emiya family left for the clearing in the mountains.
While walking shirou asked his father
"Dad I feel as if I can learn more from structural grasp except the shape, so can you get me some real swords?"
< Shirou's origin is a sword so his practising with different swords is a good idea and this can help him with his idea of making his personal mystic code that he proposed after learning about my origin bullets>thought kiritsugu and said
"I will get you some hand-forged swords and some swords with history as things accumulate mysteries with age and it is good for you to practise reading mysteries."
Nodding his head shirou shirou walked alongside his father till they reached the clearing. Running to the middle of the clearing shirou closed his eyes as the sound of a hammer echoed in his mind.
Feeling the flow of mana inside himself and the surroundings he released mana into the surroundings. Guiding the released mana into a line he enclosed about 10 feet in diameter within the mana circle.
This action alongside his intention of slashing the space inside and outside into different pieces established a bounded field.
Looking at this the older emiya smiled and said
"Excellent shirou, now that you have learnt to establish bounded fields it's time you learnt about sigils and magic circles for advanced bounded fields"
"Once established the bounded fields can't move or expand and have to be constantly fueled if they need more than just the ambient mana to function"
"Sigils are symbols which function as boosters to the original bounded fields, they can be used to expand the field or they can be carved inside the bounded fields to strengthen it."
He explained how sigils are interlinked and can weaken the field when destroyed but they regenerate with the help of other sigils when left alone. He explained how advanced bounded fields and mainly wards regenerate automatically once you stop damaging them.
After he talked more about setting up bounded fields kiritsugu looked at his son and said.
"Shirou I am giving you a task. Fortify our house by making bounded fields."
"Start with simple sensory ones and then add advanced ones as I teach you about them."
"Consider it the long-term practise and practical assignment of what you have learnt."
Excited shirou said
"I will do my best Dad"
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Shirou went to school and Kiritsugu`s phone rang, picking it up as soon as the voice on the other side said
"Greetings my friend!"
He immediately identified the caller as Altair and said with a serious tone
"Talk about what you called me for, we both know that your facade doesn't work on me."
Altair replied with a tone very similar to kiritsugu and the earlier fawning vanished like the wind
"Very well, the books about the basics of bounded fields and basics of mystic code creation you asked for have been found."
"The mercenaries you introduced to me have successfully killed my brother and retrieved half of the crest from him, hence as considering you overpaid me by doing this favour I will add the basics of runecraft."
"But don't expect it to be something good as it's shunned by most of the clocktower for a reason."
"fine, we have a deal." said kiritsugu who was about to cut the call but Altair said from the opposite end.
"Do you have any future predictions that you salvaged from the target we talked about?"
"Why?" asked kiritsugu worried
"From our experiments, we concluded that spreading prophecies done using astromancy
Increases the chances of it becoming true, so I wanted to do the same experiment to find out if the visions of mystic eyes follow the same rules."