Rin was going through what most magus go through their whole life. They all ideologies a concept of giving up humanity to become a machine to reach the root and consider those who use their powers for their personal interests as spell casters and despise them. The irony of the situation is machines in the world try to become human and humans are trying to become machines, as they say, grass is greener on the other side.
Still, after everything magi never shed their human nature and hide and disguise it under layers of hypocrisy and delusions. Rin didn't show it but idolised her father for her; he was superhuman and she took it upon herself to fulfil the man's desire after she learnt of his death in the war.
Still, what she and most mages didn't understand was that the ideal state is an ideal state because it only exists in theory and could never be practical. Rin slowly surrendered control of her circuits to shirou who had a sudden rush in his mind, he felt like he could understand the world at a glance but still grounded himself very fast as this rush due to the sudden increase in ability was not unfamiliar to him.
His clarity and thought capacity were nearly completely restored. His circuits were specialised to work with blades and hence they can take a lot of pressure compared to Rin`s as at her core her ability is being a jack of all trades but master on none while he was the opposite. Still, the quality was easily supplemented by quantity due to her having multiple times more circuits than him, pedigree is a major deciding factor in magecraft and shirou was confronted with this harsh truth in his face.
Still, Emiya Shirou was nothing if not insane, he was not affected by learning his place in the world of magi because he had etched one thing in his mind that is he should move forward at any pace because if you can't run then walk if you can't walk then crawl and if you can't crawl then roll on the ground but don't stop moving forward.
The future is scary because it is unknown and for him, it is not so. if his destination is to be murdered in despair then he will survive as the basic instinct of all life is to survive and he will survive because he has people he would like the be with a little longer.
Focusing his mind he pushed the sword into a wedge that held it still and straight. As the blade had sufficiently cooled down and was straightened enough the wedge was used to hold it still and allowed him to use both hands to work on the blade.
Using a chisel he scraped away the layer of black iron oxide and ash from above the blade, after cleaning the blade it revealed its true colour in the form of lustre of steel but its colour was relatively dull because it was mixed with various catalysts. Still, as if not satisfied shirou brought out files and began cleaning the blade of the major areas of blackness.
once the blade looked clean enough shirou removed it from the wedge and went to a corner in the shed. In that corner, the floor was raised like a pedestal and inclined from one edge to the other making a slope. This was a sharpening set-up that the teacher and student pair had derived. Here there was a water supply that allowed to easily wash the blade and different coloured naturally occurring whetstones for different levels of polishing on different types of steel.
(image of whetstones)
Putting one knee on the board the boy began to move the sword back and forth polishing it and exploding clear steel. By now it had become very uncomfortable for Rin as shirou was sweating profusely and the environment was filled with heat but she was satisfied as she felt the atmospheric mana and concluded that the stubble ritual that was taking place was unharmed.
Even when Rin pondered for a time she was unable to find out why this had happened and the unexpected was more dangerous than failure in magecraft because things out of your control meant a boon could become your bane in an instant. She can't be blamed for this as the problem arose from a completely different system than the one she practises.
The 1st component of this was the location, shirou began this on the land of Japan and drew the mana from a leyline that began and ended in Japan. The prevalent thaumaturgical foundation of this island nation where the age of gods receded very late was related to Shintoism and Taoism specially onmyodo for this case.
(A/N: a THAUMATERGICAL FOUNDATION is what Solomon gives to mankind, with the disappearance of gods at the end of the age of gods mages lost the convenient vessels of powers connected to the planet hence their spells lost power, for example, the spell that used to produce fire as hot as the sun now made the greek magus faint due to mana exhaustion by casting a candle flame.
It happens because Apollo the passage for the spell is no more and Gaia can't understand what the magus wanted to change in her texture. Hence Solomon the king of magecraft developed thaumaturgical foundations that made the beliefs of mankind imprint on the leylines of the area they are present. Now these systems become the vessels of power rather than the gods.
Now these foundations have become the reference for gaian and act as an input and output chart for it to allow mage craft. Well but if the gods were dedicated internet encyclopedias on particular topics( divinity they held) the foundations would be paper dictionaries hence the mage craft became weaker like the people who used to visit wiki and search in AC rooms with high-class wifi are now forced to skim through broadly divided dictionaries in candlelight.
The alternate version of this system is the philosophy keyes and the thought magecraft that we will discuss later.)
2nd component was the smith himself and his art, the smithing technique that he used originated from Muramasa school which was infamous. It was believed that the smiths of this school were mad craftsmen obsessed with their craft so much that the blades they crafted were infused with their crazed passion and became cursed. In magus terms the muramasa style of forging blades with negative attributes which the native supernaturals called "demon blades".
3rd component was the nature of the katana. Swords are considered talismans and vessels of the kami, they are kept in shrines and represent protection. They are believed to contain spirits and have a will of their own. The Shinto gods are known to be volatile and more involved with mortals by giving them blessings and boons, but the way to connect with them is eccentric. Rather than worship the divine spirits are moody and prefer indirect forms of reverence like organising games, sports, festivals and rituals in their name.
So when an objectively insane smith poured his desire to succeed in forging and began making a blade considered a sacred talisman inside a room connected to a ward directly connected to a leyline the trouble began. The unstable mind of the smith began seeping into the blade and it reached the threshold of creating a spirit of nature that is called a demon or evil spirit.
The ward became the temple, the smithy became the shrine, rin and kiritsugu became the spectators and wetness, the creation of the mystic sword became the attempt to birth a demon in a protective talisman and this process became a way to commune with the divine hence making the prior step into a ritual with the blessing being the birth of a cursed blade, not a mystic code that just applies gandr from a distance but a blade conceptually imbued with the curse.
Shirou rubbed the bade on the stone and then when it was satisfactory for his liking he put the blade on a stand brought the boxes to his side and placed a marble plate just below the blade.
He brought out two and put them on the magic circle carved on the floor. The pair of children had carved the circle that increased the mana concentration in 3 locations in the smithy, 1st was in front of the forge, 2nd below the seat where shirou was currently sitting and 3rd was near the table filled with wood and materials for handles.
(image of the magic circle)
(A/N: so people hoe was the chapter, those that couldn't understand the magecraft can ask in the comments. I am using the nasuverse official terms for stuff so some words might not neat mean what you imagined. We are moving into the rabbit hole and I tried to make the explanations simple and concise, as a lot of people here are likely anime only or understood about fate from fanfics and have never read any source material in its original form.
And fgo players should be clear about the demon blade thingy, the lore was actually funny af but the demon blades there refer to blades on the level of divine construct made by a human, ex Musashi's sword that Muramasa himself admits to have been too much and he pushed it into the class of spirits( this means the stuff like divine spirits, great mother or father class fairies, dead apostle ancestors (the remake ones) and etc)
But the blades forged by shirou have like natural negative attribute spirit inside them, like Rin`s gems have a natural spirit inside them.
.
.
.
.
.
.
THANKS FOR READING:)