Overview
Though Shirou Emiya appears as a perfectly regular japanese high schooler, he is actually a fledgling magus -- a magic user. Calling him a 'magus' might be considered generous by most people, however, on account of his magecraft being limited largely to reinforcement of objects and his own body. Either way, his evident ineptitude is not enough to stop him from putting his all into helping people around him, and pursuing the dream of 'becoming a hero of justice'. After a ritualistic battle for the right to a certain wish-granting relic went horribly wrong, Shirou has been shunted to the World Tree, and even that has not put a damper on his kind, naturally helpful nature -- still willing to help anyone who needs it, even while he is chasing after the answer to the question of what became of the world he left behind in the wake of the potentially-catastrophic event.
Perks
Melee Combat: Basic ability to fight with swords and fists
Though Shirou is hardly an experienced warrior or a trainee of martial arts, Shirou does have some experience in brawls and basic training with swordsmanship. This combined with his own physical conditioning does lend to him being able to hold his own in a fight. However, his experience with 'real' combat is limited, so while he might be able to hold his own, directly attempting to directly take on a more experienced martial artist or swordsman is beyond his capabilities.
Archery: Shirou is proficient in the use of bow and arrow.
Shirou is practiced in the use of a bow and arrow, and possesses almost prodigal accuracy with them. His experience is largely translated from an archery range, however, and his skill has little actual combat application if put under pressure in spite of his accuracy.
Magecraft (Reinforcement): Enhancement of objects and his own body and eyesight.
Shirou can use his somewhat unorthodox method of channeling magic to enhance objects he has touched and analyzed. He mostly uses this kind of magic to increase the durability of any given object, though in theory he can also directly increase the effectiveness of an object in it's primary use (like making a blade cut more effectively), but due to his inexperience, he has more limited success with this manner of use. He can additionally use Reinforcement directly on his own body's physical capabilities, though to a lesser extent than a more experienced mage with better mana reserves would be able to -- with the exception of when applied to his eyesight, able to Reinforce it to see objects accurately nearly as far as four kilometers away.
Magecraft (Structural Grasp): Magical analysis and understanding of physical objects' structure/composition
Shirou can touch any object and analyze it in his mind, akin to creating a phenomenally accurate blueprint in his mind. This does take some time, and more with larger and more complex objects; but given time, he can understand the composition of anything he analyzes with great accuracy, to the point that after several uninterrupted minutes, he can even form a map of a large mansion in his mind, including the furniture and people present in any given rooms. The sliding time expenditure requirement seems to be exempt from his analysis of swords and other similiar close combat weapons; Shirou can instantly analyze swords just by looking at them. Analyzing an object with Structural Grasp does, however, require the object to be made with materials and concepts that exist within human understanding; a sword made with materials existing outside of the physical World, for example, is something Shirou cannot analyze.
Regeneration: A magical regenerative quality -- but with a risk.
An artifact implanted into Shirou's body to save his life continues to provide magical healing to his body. Normally the artifact would function at a significantly reduced capacity without the proximity of it's original owner, but the magic has been directly affected by his own magical affinity of 'Sword' to create an unique form of self-healing; taking form of small blades materializing over damaged parts of his body to protect them from further damage and knit wounds closed. While the magic allows Shirou to survive injuries and trauma that would normally kill him, it does not function quick enough to prevent him from being knocked unconscious from severe enough injury, and destruction of his heart or brain is still instantaniously fatal. More over, due to the magic relying more on his Origin over the relic, it holds an inherent risk of going haywire; heavy damage inflicted on his body has a chance of causing the blades to form incorrectly and stabbing through his body instead.
Magecraft (Tracing)< Edge-E Copy-T >: Magical recreation of weapons and channeling of their "history".
Shirou's unique take on Projection magic, "Tracing" allows Shirou to not only copy weapons he has encountered with natural ease, but also copy and channel the "History" behind the weapon. In practice, this means that Projection of a weapon instantly gives Shirou the proficiency - but not mastery - to wield the weapon and the ability to use the techniques employed by its past user while it is being projected. This extends even to magical weapons and their supernatural qualities -- though such weapons are typically traced at a lower quality compared to the original and require significantly more effort and mana to the point that Shirou can normally Trace only one such weapon within a short time, and even then he risks unhealthy strain on his physical body. Performing techniques that require supernatural physique, while possible, is even more dangerous, to the point of resulting in unpreventable damage to his body when attempted and requires spending <Edge>. In theory, Traced weaponry could be launched telekinetically as projectiles instead of being wielded in a hand, but such a feat would require more mana than Shirou possesses. Firearms and other weapons that work with complex machinery are incompatible with Shirou's affinity, and cannot be Traced.
Kanshou And Bakuya< Edge-E >: A pair of enchanted swords Shirou can Trace reliably
A pair of curved short swords Shirou can project reliably and consistently. Despite being classified as magical weapons, he can project them with a much more bearable mana cost and less effort than normal, and even the 'skill' carried over with them seems to resonate much more naturally with him. The swords themselves are of remarkable quality, with low-level enchantments that allow somewhat easier damaging of supernatural creatures over mundane weaponry, and possess an "attraction" to each other that allows one sword to fly back to it's wielder as long as it's compatriot is held by him. Spending <Edge> allows Shirou to draw more deeply from their history, and in combination with Reinforcement he can momentarily project an improved version of the blades, enhancing their quality even further and significantly increasing their damage output to supernatural creatures.
Complications
Dangerously Unorthodox Magus: Shirou's magecraft is outright dangerous, and he overextends himself too easily
The core of Shirou's magecraft method is at best unusual, and at worst horribly wrong. He is effectively putting his body at risk every time he works magic, and even in the best case scenario causing physical strain on himself. Shirou also mistakenly sees nothing wrong with this, and merely considers it a cost of wielding magic -- and he effectively has no hesitation whatsoever on paying that cost either. As a result, Shirou overextends himself and overuses his magic much too easily, and if pressed into a situation where he sees it as a necessity, he will end up suffering severe damage to his body.
Distorted Sense of Self: Shirou is unhealthily selfless
Frankly, Shirou is spiritually broken. Only able to derive any sense of self-worth from the joy of others rather than himself, he constantly strives to help others -- even at his own expense. He is easy to sway to doing favors for others, no matter how much they might inconvenience him, and he will outright dive into danger to help someone without a second thought, no matter how unsensible or suicidal it might be.
Foot, Meet Mouth: Shirou has an unfortunate habit of letting slip inappropriately blunt things
While Shirou isn't entirely socially inept, he has... bursts of odd choices in the way he uses words, sometimes. He sometimes is all too direct and blunt when speaking, and even finds himself saying akward truths to people that should perhaps be left unsaid. Shirou does additionally have a bit of a sarcastic streak at times, but his poor conveyance of body language easily results in people taking his words at face value even then.