"I'll just come out and say it on behalf of Author-san.
Reality Marble… Territorial Expansion… Magus… Sorcerer… Can create cursed weapons… Can utilize cursed weapons…
It just makes sense."
(-)
This body is made of blades…
For as long as he could remember, all he wanted to do was be able to smile like he did back when they first met. He was born from the tainted fires of the fourth Heaven's Feel, and raised by the dying shell of the man who was known as the Magus Killer.
Iron is his blood…
He was fundamentally broken, forever lacking that which would make him human. Emotions were not something he felt, merely emulated for the sake of appearances.
And glass is his heart…
Self-preservation was not something he could comprehend, for he saw no value in his own life. All he ever desired was to save others even if it wound up hurting him.
He survived through countless battles…
There would be no meaning to his life if he couldn't save everyone. This ideal had broken the man he could have been.
Never retreating…
Yet through some miracle, he managed to survive in one piece, regardless of how many cracks were left over.
Never victorious…
Though the question still remains; does this make him less than human, or something more?
(-)
Dull gold-colored eyes snapped open as he regained consciousness. It was only for a moment, but the brief blackout was long enough for him to look back at everything that led to where he was now. His right arm felt like it had just been hit by a steel beam, while his left arm was beginning to feel numb. The broken pair of Chinese falchions dropped from his hands as a new pair took their place. Blood from a cut on his arm dripped down onto the white blade and marred the pristine metal with a smear of crimson. His legs were trembling from exhaustion, but he refused to let them fall. If he were to give up now it would result in certain death. Not only for himself, but for the two children that were cowering behind him for protection.
"Geh, hi, hi, hi~!"
He leveled a weak glare at the thing responsible for their current situation. All that did was result in the four-eyed freak chuckling in amusement once again. Although it bore a humanoid shape, the creature was anything but. Its skin was beyond the point of just being a sickly-pale color and slightly translucent, almost as if it were a corpse that had been left to float in the water. The water-like nature was further emphasized by the amphibian webbing between their fingers and the gills on its neck. The connection it held with water showed in their surroundings as well. If Shirou didn't have one himself he might have believed that he was in a Reality Marble, however it was lacking in several aspects that leaned towards it being more of a failed attempt. The bog they currently stood in did change in response to the creature's actions, but it was not all-powerful. If that were the case, he would have been dead the moment he stepped inside the barrier.
No, this was less of a manifestation of the soul and more like an artificially created home-field advantage.
Shirou blinked his eye as blood dripped into it, the monster so self-assured of its victory that it did not even bother taking advantage of the momentary distraction.
"Alright then. Let's see if you can handle what I throw at you next." he muttered as his grip on his swords tightened. "I need you two to run as far away as possible and try to escape. Things are about to get a lot more dangerous." He then instructed the children behind him. Moments later he could hear the pitter-patter of hurried footsteps as they fled.
The monster paid them no mind for the moment, intent on finishing him off before giving chase. Trying to be tactical about his approach was getting him nowhere in this fight, as the creature couldn't care less about fighting properly. Its movements were unnerving in how its body would twist and contort at impossible angles, like it lacked bones or something, and fade into the fog before jumping out for a surprise attack. If Shirou was going to survive the fight, he would just have to brute force it. But that also meant pinning the creature down long enough to land a killing blow.
"Spirit and technique, flawless and firm."
Hurling the first set of married blades at the monster's neck, Shirou promptly traced another pair even before the first were knocked off-course by a strong slap. Lunging forward, he quickly traced a Black Key and fired it off with little preamble.
"Our strength rips the mountains."
Jerking its head to the side, the monster avoided the Black Key but was nicked in the sides by the second pair of falchions that followed behind it. By now the first pair had already started their return trip, which the creature caught out of the corner of its eyes.
"Our swords part the rivers."
Performing a backflip, the creature managed to avoid the first set of spinning blades, only to be struck by the third pair Shirou had thrown. With the first set returning to his hands, the magus then fired off several more Black Keys.
"Our names reach the Imperial Villa."
Stuck in mid-air with no direction to dodge with the blades spinning around it, the creature was forced to catch two of the swords in its hands, managed to block one by raising its foot to kick it away, but the final Black Key found purchase in its stomach.
"The two of us cannot hold the Heavens together."
With its movements momentarily restricted, Shirou broke the pair of swords in his hands before reconstructing them into a larger pair that resembled black and white wings. The four remaining falchions flying through the air each came back and sliced into the joints of the beast's limbs.
"Kakyoku Sanren!"
Black and White wings clashed against the creature's body with immense force and cleaved into its flesh.
"GYYIIIIIIIIIIIIIIIIEEEEEE!"
It let out a pained scream as the spinning blades shredded apart its limbs and the metal wings carved their way into its chest cavity. A black liquid substance that constituted its blood was splattered into the murky waters beneath, arms and legs soon joining the former as they were lopped off.
"RAAAAGGHHHHHH!"
With a primal roar escaping from his lungs, Shirou pushed forward with his remaining strength and managed to slice clean-through the creature's chest. However, he wasn't done yet. Dropping the white falchion and grabbing one of the Black Keys, he thrust the blade upwards. The tip of the blade pierced through the monster's neck and exited out the top of their head. Collapsing to the ground, the creature was no more, and its body sank into the quagmire. It was not until the world around him began to fade that Shirou allowed himself a moment to breathe. The swamp vanished, the surroundings reverting back to being a small creek along the forest tree line.
Dropping to one knee, Shirou utilized one of the married blades to keep himself upright. It was a great relief that he finally managed to kill whatever that thing was, but he was still severely injured, exhausted, and in need of medical attention. Lifting his head up, he spotted something that was out of place. Staggering forward, he reached out and picked up the object. Upon inspection it was obviously a human finger of some sort, but Shirou could tell that there was something extremely wrong about it. Besides being strangely well-preserved -indicating it wasn't from a recent victim- it absolutely reeked of being cursed. Still, whatever the finger was, it was clearly responsible for the creature he had just killed. It had to be destroyed.
Lifting his hand while trying to find a blade that would be capable of eradicating such a powerful curse, he cried out in pain as he felt Archer's arm violently reacting beneath the crimson shroud. That last fight had him draw on more strength from the arm than what he could normally handle. Dropping the severed finger, he grabbed at his shoulder and tried his hardest to 'will' the arms influence away.
"Damn it! Not now!"
Falling to the ground he could do nothing other than writhe in agony and try to outlast the pain. The only silver lining to the situation being that he hadn't needed to remove the shroud during the fight, otherwise his condition would be considerably worse.
"Gotta… find those… kids… Make sure… they're safe…" he groaned out through clenched teeth as he tried in some futile attempt to push himself off the ground.
"Don't worry about them. I made sure they got home safe and sound."
Snapping his gaze up, Shirou was surprised at the sudden presence in front of him. Even in his current state he didn't think he'd miss someone approaching. The man standing before him was dressed in black and had a blindfold wrapped around his eyes.
"Who are…"
"Not important right now." the man spoke as he interrupted Shirou's question. "You look like hell kid. Take a breather, you earned it."
With his adrenaline running out and the pain too much to withstand any longer, Shirou was forced into unconsciousness. He could only hope the newcomer didn't have any malicious intentions toward him.
(-)
The answer is neither. Shirou Emiya has forever been and will forever be naught but a Sword.