High School DxD: Fate's Error

"Punch faster."

"Punch harder."

"Punch—are you even trying?!"

The grating voice tore through the rhythmic thwack of my fists slamming into the tree. My jaw clenched, and I shot a murderous glare at the old man sitting on a nearby rock, leisurely munching on a bright red apple. He chewed thoughtfully, watching me like I was some sideshow act, utterly unbothered by my suffering.

My knuckles were raw, split open from days—no, weeks—of this madness. Blood smeared the bark, mixing with the dents I'd carved into it through sheer force alone. Every nerve in my hand screamed in protest, but I ignored it. I had to.

"Keep going," he muttered darkly, his voice carrying the kind of weight that settled deep into my bones.

I exhaled sharply, blinking sweat out of my eyes as I forced my arms to move again.

It had been two months. Two fucking months since my old life ended and this brutal, soul-crushing reality began.

And I hated to admit it… but I was changing.

The old man was no saint—hell, he was a sadistic bastard—but he was right.

Since the day we first sparred, I realized something:

I fucking missed reading.

At least with reading, I could relax, maybe have some tea, enjoy a slow afternoon. This? This was non-stop punishment. Pain was my only companion now.

Even with my adaptation ability, the agony never truly went away. It dulled, sure, but my body still felt every ounce of fatigue, every splintering ache. Adaptation worked best for increasing my endurance—it didn't magically erase my suffering. Each strike against the tree sent fresh jolts of pain through my arms, my punches growing slower, weaker.

I could barely keep my balance. My body was trembling from exhaustion.

"Keep going, brat."

I growled under my breath. "I heard you the first damn time."

He smirked. "Oh? You sure? Because that last punch was pathetic."

A surge of anger flared through me. With everything I had left, I twisted my hips, put my full weight into my next punch, and slammed my fist against the bark. A deep, resounding crack split through the air.

The tree splintered.

I hissed through my teeth, shaking out my battered hand. The skin had torn in a few more places, fresh blood trickling down my fingers, but I didn't care.

The old man whistled. "Not bad, kid. Not good either, but at least you don't look like a complete embarrassment anymore."

I shot him a withering look.

"You know," he mused, leaning back against the rock, "back in my prime, people begged me to take them as students. Even the Pope himself wanted me to train someone."

He paused, gaze flickering with something unreadable before he shook his head. "Point is—put yourself through hell now, so you can live in heaven later."

He said it so casually, like it was as simple as breathing.

The worst part? I knew he was right.

As much as I wanted to punch him square in the jaw, I couldn't ignore the fact that I had been weak. My age had made me arrogant. I had grown up in a world of convenience, unaware of what real suffering was.

The old man once told me:

"A man with too much pride is already halfway in the grave."

And now, I was starting to understand what he meant.

"Alright, kiddo. Break time."

Relief flooded my body so fast I almost collapsed on the spot. My legs wobbled as I stumbled toward him, holding out a hand expectantly. He chuckled, tossing me an apple.

I bit into it immediately, moaning in delight.

How bizarre.

A few months ago, I wouldn't have given a damn about something as simple as fruit. Now? This apple was the best thing I had ever tasted.

The old man reached out, casting a warm, golden glow over my hands. I winced as the wounds stitched themselves back together, the pain fading almost instantly.

I stretched my fingers, sighing. "Ahh… that's the stuff."

He nodded in silence, gazing out over the rolling green hills. The Irish countryside stretched for miles, bathed in the golden hues of the setting sun. Despite everything—the grueling training, the exhaustion—this view never failed to take my breath away.

Then—

"I suppose it's time to increase the weight of your seals."

I choked on my apple.

"Already?!"

He smirked at my reaction before tracing a glowing rune in the air. The seals on my body activated, and my entire world shifted.

My knees buckled. My muscles screamed.

The sheer weight pressing down on me made me grit my teeth as I adjusted, forcing my stance to hold firm.

Over time, I had learned to handle these weight increases. The first time had nearly broken me—my body had collapsed under the pressure. Now? It was still brutal, but I recovered faster.

"In two days, I'll be leaving for a week."

The words hit me like a brick.

"Leaving? Why?"

He exhaled slowly. "I have a mission."

My stomach tightened. "What kind of mission?"

"I can't tell you yet, kiddo. But it's important." He ran a hand through his graying hair. "While I'm gone, I expect you to stay disciplined. We're in a safe location, but if anything happens, go into my room and grab a map. My seals cover a twenty-mile radius. If a red dot appears on the map, that means something evil has infiltrated our territory."

His eyes darkened. "If that happens—do nothing. You may be stronger now, but you have no battle experience. And that is all that matters in a fight. Do you understand?"

I swallowed hard and nodded.

"Good. That said, there haven't been stray devils in weeks. The odds are low—but not impossible. If one appears, I'll deal with it when I return."

He hesitated before sighing. "I apologize, kiddo. When you're stronger, I'll explain everything—why things are the way they are. Especially with me."

His voice softened, and for the first time, I caught a glimpse of something deeper in his expression. Something almost… regretful.

He ruffled my hair, smirking. "For now, just focus on getting stronger."

I nodded, but internally—

One week to myself…

Fucking jackpot.

I barely managed to contain my excitement. After two months of this hell, I deserved a break.

Even if just for a day.

Then—

"Alright, enough of the break. It's squatting time."

I groaned as he casually picked up a 1.5-meter log that weighed a goddamn ton before placing it on my shoulders.

"Lightweight, son!"

"Lightweight, baby!" he chanted with glee.

I glared. "I swear to God—"

But I was already sinking into the squat, my quads burning, my body screaming.

As I struggled, he grinned.

"Great technique, kid. That's 500kg now. Not bad."

I collapsed onto the ground.

"I can't walk."

He just laughed, healing me again.

Then—

"Alright, time to run home."

My soul left my body.

My eyes blazed.

"YOU OLD BASTARD—"

I shot forward at full speed, chasing after him as he laughed into the evening air.

My lungs burned. My legs felt like lead. The added weight from the seals made every step a battle, but there was no way in hell I was skipping dinner.

The old man was already leagues ahead, sprinting down the hillside with the energy of someone half his age.

"Hurry up, kiddo!" he called back, laughter in his voice. "Or no dinner!"

My vision tunneled.

No. No, no, no.

He wouldn't.

Would he?

Something primal awakened inside me.

"LIKE HELL YOU ARE TAKING MY FOOD, YOU OLD BASTARD!"

A second wind exploded through me. I dug deep, pushing my body beyond its limits, forcing my legs to move faster. The wind howled in my ears, the world blurring around me.

I was gaining on him.

Twenty feet.

Fifteen.

Ten—

Then—

The bastard tripped me.

One moment, I was running. The next, the ground was gone, and I was airborne.

"OH, YOU—"

Gravity kicked in.

I crashed into the dirt, rolling down the hill in a violent blur of limbs, pain, and loud, very unmanly screaming.

By the time I landed at the bottom, I was a heap of aching muscles and bruised dignity.

Above me, the old man stood with a victorious smirk, tossing an apple in his hand. "Lesson of the day, kid—"expect the unexpected."

I wheezed. "You... are... a menace."

He only shrugged. "And yet, you keep listening to me."