When the Hero is not a Hero(Fate/Stay Night x Disgaea)
Prologue: Evil's Miscalculation, Good's Loss - The Future Hero takes a Wrong Turn

Suffering

Angra Mainyu, All The World's Evils, was content.

Pain

The Fourth Holy Grail War came to a close and everyone involved had a healthy dose of pain and suffering.

Despair

No survivors, exactly how the evil incarnation wanted it.

Defeat

While the destruction of the ley line was going to be a huge pain in his evil backside, it'll only mean that he'd be forced to conduct the Fifth War earlier than normal. And the chance to bring about death and destruction ahead of schedule was a good thing in his evil book.

But amidst the chaos, amidst the blazing inferno that is swallowing the city piece by piece, a lone child could be seen, making his way through the flames. The boy will die soon, that much was obvious. But the fact that something survived the flames created by he, Angra Mainyu himself was not to be tolerated. In a fit of impatience and rage, the avatar of evil decided to send the child to hell. But the rashness of the act caused some miscalculations on Angra Mainyu's part. For someone who prided himself to be All the Evils of the World has forgotten just how many hells exist.

Somewhere else...

A blue haired child with large hair antennae and a billowing scarf was trying to persuade a white haired boy that the blue haired child was the white haired boy's father. Keyword being trying.
Beside the blue haired boy was a red haired woman, who, in what passes to be a motherly tone, claims that she is the white haired boy's mother. What nobody expected was for a red haired boy, about six years of age, to appear before them, barely conscious just as the red haired woman was talking.

"I am your mother..."

The red haired boy and the red haired woman stared at each other.

"You're my mother?"

Suffice to say, everyone present but one were amused.

-

An indefinite amount of time later...

Etna, Prince Laharl's seemingly loyal vassal was chasing a red haired teenager across the streets of the Makai, clutching a spear in her arm and a horde of blue penguins following her.

"You're dead! You hear me? DEEEEAAAAD!"

The teenager laughed as if hearing death threats from his mother was a common occurrence.

"What are you gonna do about it, old lady?"

Etna snarled, a sound that most definitely wouldn't come from a lady, erupted from her lips. She plucked the
closest penguin from the ground and hurled it at the boy.

"Today's dish: Shirou, flambeed in Prinny oil!"

The explosion rocked the entire kingdom. And when the smoke cleared, the boy, now known as Shirou, was gone.

-

Shirou, no last name, had done many things. Blew up Prinnies, angered Etna, mooned Laharl, angered Etna, groped Flonne's butt, angered Etna and angered Etna. But despite all that, his mother never actually blew him up with enough force to blast him back to Earth.

"Hmph. She must've been really angry. I'm not sure whether it's because I stole her panties or convinced Laharl to steal her Sea of Gehenna Pudding. But no matter. I've heard that there are powerful heroes of justice here on Earth. I'll just beat them up until I'm at a high enough level to kick my mom's ass! MWAHAHAHAHA!"

And as Etna's child, adopted or not, it wasn't surprising that his luck would bring his laughter to the attention of the red clad archer and the blue clad lancer that was having an epic fight to the death several meters away.

-

Shirou wandered the streets aimlessly, a bit annoyed at the wound in his chest. The guy in blue seemed to think it was a good idea to pierce his heart with a lance. Shirou didn't know how long he was unconscious but he vowed to exact his revenge on that spearman or he'd eat a Prinny.

"Tch. Didn't he know that he can't kill me? I'm the protagonist of this story. There's no way that a borderline homo like that is going to strip me of my screen time."

He stopped at the edge of a field that looked like it was razed to the ground several years ago. A feeling of dread permeated the area, enveloping the entire place with a gloomy atmosphere. Shirou gazed at the field in awe.

"This place is perfect! The murderous aura surrounding it reminds me so much of mom that I wouldn't be homesick!"

He clapped his hands and a group of Prinnies appeared before him. Five minutes later, a massive mansion stood in the middle of the defiled ground.

-

The spearman stared at the annoying brat in front of him. He tracked down the kid, who so rudely survived his attack, and found out that the kid lived alone in a mansion smack dab in the middle of a tainted field. It was disconcerting, to say the least, but he had to act like the cool and collected guy that he is.

"Nothing personal kid, but I'm gonna have to kill you."

Shirou scoffed at the obviously minor character. Every story always had a character that allowed the protagonist to show his awesomeness.

"Mwahahahaha! I'm already at level 700! You dare challenge my power?"

The spearman frowned. This kid was treating life as one of those modern day video games? Well, the kid was going to die anyway so might as well let him have his fun.

And thus, it was to Lancer's surprise when the kid blocked his prized weapon by a spear that looked flimsier than a rolled up poster.

"Hah! Feel the wrath of the cheapest spear ever!"

Shirou thrust his spear again, forcing Lancer to step to the side just in time to hear a squeaky "Dood!" before his face was ravaged by a rabid penguin wielding two knives.

"What in Scathach's name?"

The rest of his words was left unheard as the penguin blew up in his face, sending Lancer flying out of the house. Shirou followed his assailant's trajectory to see Lancer glaring at him.

"I was going to grant you a painless death, but now I've decided to make you suffer!"

Shirou shrugged. He'd had worse threats from Etna after all. Lancer lunged at him again, only to be repelled by the sudden appearance of a blond woman wielding an invisible weapon.

"Hey! Where'd you come from? You're stealing all the spotlight!" Shirou yelled. The blonde stared at him with wide eyes before visibly composing herself.

"I ask of you. Are you my master?"

Her master? What the hell is this girl talking about? Wait, could it be?

"Hah! And Etna says I'll never have a vassal of my own! Take that, you old prune!"

It was at that moment when a murderous intent rooted Lancer, Saber and Shirou to their spots.

"Old prune, am I?"

Prinnies flew, explosions occurred and a blue clad Lancer blasted off at the speed of light. Several meters away, an unsuspecting brunette magus and her red clad Servant faced the same fate when a stray airborne penguin found them.

"Watch out, Dood!"

Cue Prinnyplosion.