Shirou Emiya lived a relatively normal, happy life for his first five years. All that changed abruptly when Kiritsugu Emiya won the Fourth Grail War and rejected the grail, causing a massive fire that wiped out his residential area. He wandered through the devastation for hours upon end, watching people die senseless deaths. Kiritsugu himself eventually rescued him, and implanted Avalon inside him to prevent him from dying. Kiritsugu would later adopt Shirou, raising him as his son and teaching him magecraft. Five years later, Kiritsugu would pass away, leaving his dream of being a hero to Shirou.
Shirou had developed a more twisted personality than Kiritsugu, and tried to protect and help everyone. After about five more years practicing magecraft and fixing heaters, the Fifth Grail War starts. At the outset, he gets attacked by Lancer and dies. Rin comes across him as he's dying and uses magic to heal him, making him basically a zombie. He summons Saber, and enters the war. During the course of the Unlimited Blade Works route, he allies with Rin for the duration, which eventually develops into a romance. Over the course of the war and through his interaction with Archer, he learns Projection and matures.
After defeating most of the other Servants, Archer and Shirou fight. Shirou wins, as his determination to uphold his ideals firmly puts him on a different path than his future self. He and Rin then form a contract so that he can use his reality marble at will, and they confront Gilgamesh, who is trying to summon a corrupted grail to kill off humanity. Shirou invokes Unlimited Blade Works and wins, while Rin rescues Shinji, who had been forcibly made into the core of the Grail. After they graduate, Shirou follows Rin to the Clock Tower and beyond, as her apprentice/manservant/boyfriend.
Battle vs. Kei Munakata (by Leolab)
“TRACE ON!” Shirou Emiya yells as he sidesteps a slash from a katana, which embeds itself into the ground. Kei Munakata simply releases his grip on the weapon, and draws another one, seemingly from nowhere. The orange- and blue-haired youths clash again in the street, the katana meeting one of Shirou’s projected shortswords while the other aims at his assailant. Kei dodges the blow and kicks back, dropping his katana.
“Please, come with us,” Shirou shouts, trying to get his foe to listen in the reprieve, “The artificial magus program is dangerous!”
“Artificial magus?” Kei says, “If you’re talking about the Flask Plan… that’s already been shut down.”
Breaking the lull, Kei draws a pair of massive hammers and charges Shirou, aiming to smash him between them. Shirou throws his shortswords at them and then projects a new pair, barely parrying the blow. Kei drops the hammers and leaps back, drawing and throwing an axe at his foe in midair. Shirou, still reeling from the shock of the prior blow, is unable to get his guard up in time to block it.
“Gandr!” Turning to look at the yell, he sees is partner, Rin, firing off a spell to deflect the axe. “Pay attention, Emiya-kun!” She yells, admonishing him while fending off her own foe, a young man with blonde hair. As she dodges a kick, Shirou turns back to his fight, and sees a boomerang being thrown at him. He crosses his swords to block, and throws them at Kei. As the swords travel in an arc, drawn to each other by their magnetic properties, he projects a bow, as well as the sword Caladbolg.
I can only do this once, so this better work… he thinks, compressing the sword into an arrow shape. He draws and lets loose, aiming at Kei’s leg. Kei ducks under the swords, twists to dodge the arrow, and charges Shirou, holding an outstretched spear. The exploding sword behind him adds momentum, and he rapidly closes the distance. “Rho Aias!” Shirou shouts, projecting a four-petaled shield. The spear is stopped cold, and Munakata lets go of his spear and creates distance again.
Faster than Shirou can react, he draws a pair of handguns and starts firing. Shirou stands firm, and the shield’s concept of “repelling all projectiles” holds. Kei completely unloads the magazines, and tosses them aside. His eyes shift to his friend’s match, and they glint maliciously. “Zenkichi, jump back a bit!” He yells, pulling out a new weapon and taking aim at Rin, who had just overextended.
Recognizing the device where she doesn’t, Shirou drops the shield and runs between them. He hurriedly puts it up again, but in his haste it only has two petals. He hurriedly chants the incantation for Reinforcement as Kei draws slack form the trigger. He fires the bazooka, and the warhead collides with Rho Aias. The explosion overpowers the reinforced Noble Phantasm, breaking it. Kei seizes the chance, and strikes, slicing into Shirou’s shoulder before he can project his weapons again.
“I am the bone of my sword,” Shirou says, desperately fending off Kei’s attacks, “Steel is my body and fire is my blood.” He dodges another blow and strikes back, his blades deflected. “I have created over a thousand blades. Unaware of loss, Nor aware of gain.” Kei draws a kusarigama and wraps the chain around Shirou’s weapons, disarming him. “Withstood pain to create weapons, waiting for one’s arrival. I have no regrets.” Shirou projects a new pair of swords, blocking a swipe from Kei’s spiked staff. “This is the only path. My whole life was Unlimited Blade Works.”
The area around Shirou glows white, as he imposes his Reality Marble over the world, drawing both himself and Kei into it. Kei, taken by surprise at the shift, glances around. He and Shirou are now standing under a red sky, on a hill filled with swords stabbed into the ground. Shirou extends his hand, launching a barrage of swords at Kei. The onslaught obscures him, and Shirou stops, feeling something’s off. As the dust clears, he sees that the swords had crashed into a massive pile of weapons, and his foe was nowhere to be seen. At that moment, a fist crashes into his back, spinning him around and breaking a rib.
He sees Kei for a split second, until he vanishes again. Acting on instinct, he summons a sword to block the kunai slicing towards his neck. A split second later, he summons another sword at his side to block the axe Kei had swung. In pain and panicking, he creates a whirlwind of weapons to give himself space, unable to track his foe’s newfound speed burst. Kei stops moving for a split second, baiting an attack.
The bait works, and Shirou sends a storm of swords towards him, maintaining the defensive whirlwind around him. Kei vanishes from his sight, moving too fast to see. He penetrates the barrier, taking only superficial cuts from the spinning blades, and slams his palm into Shirou’s shoulder, dislocating it. He grabs his foe’s other wrist and twists, snapping the elbow joint. An uppercut fractures Shirou’s jaw and lifts him off his feet, knocking him unconscious in the air. As Unlimited Blade Works fades, Kei draws a pair of knives and stabs them into Shirou’s hands, crucifying him on a wall.
Kei steps back from his victory, confirming that Zenkichi had won over his own opponent, before noticing the presence of several other people; while he was in the Reality Marble, the rest of Zenkichi’s friends had arrived. “I told you he was alright,” the blond-haired youth says, rushing towards him.
“I’ll leave the rest of this to the Student Council, then?”
“We’ll take care of it, Munakata-Sempai.”
When it comes down to it, this match was about passive abilities versus active abilities. Kei's abilities were passive, which means they were always on, while Shirou's were active, which means he had to consciously determine when to use them. Despite Kei's abilities being "weaker", the fact that they were always active - especially his trump card of super speed - were always active pulled the match in his favor.