High School DxD: Fate's Error

"Splash!"

The sensation of icy water against my skin jolted me awake, and I flailed wildly, gasping for breath as my body registered the freezing cold. Heart racing, I whipped around, drenched and furious, to see the culprit standing smugly at the doorway.

"What the hell, old man?!" I shouted, clutching the soaked blanket.

The old man—my so-called mentor—stood with a dented bucket in hand and the smirk of someone who knew exactly what he'd done.

"Good morning, Oscar!" he declared, far too cheerfully for this hour. "Think you can just relax in your sleep? Not anymore, son. From now on, sleeping peacefully is a luxury of the past. The sooner you learn to sleep prepared, the better."

"You psycho! What even—" I stammered, shivering. "This is insane!"

"Is it?" he countered, raising an eyebrow. "Do you think a vampire would politely wait until you're awake before sinking its teeth into your neck? Do you think a devil would give you the courtesy of a warning before they cast a fireball at your back?"

I wanted to argue, but my teeth were chattering too hard to come up with a rebuttal. Grumbling, I stomped toward the kitchen, wringing out my drenched shirt along the way. The cold lingered on my skin at first, but as I moved, something strange happened—it started to fade. Warmth began radiating from deep within me, pushing back the icy chill.

The old man's voice cut through my thoughts. "Hmm. Adapting already, are we?" His tone was equal parts fascinated and impressed. "That's quite the useful ability. Your body seems to be acclimating faster than I expected."

I rolled my eyes. "Great. Glad to know I'm a science experiment."

He set a steaming cup in front of me, a crooked grin on his face. "Here. Tea."

I stared at it. "Got any coffee?"

The grin faltered, and for a moment, he looked genuinely wounded. "I pegged you for a tea man…" He muttered something under his breath as he shuffled back to the counter, and a minute later, a mug of coffee was slammed down in front of me.

"Happy now?" he grumbled.

"Ecstatic," I deadpanned, taking a sip.

We sat in silence for a while, watching the sunrise through the kitchen window. The early light spilled across the table, and for a moment, it was almost peaceful.

Then, true to form, the old man shattered the calm. "Right!" He clapped his hands and shot to his feet. "Time to get to work. There's much to learn, and time waits for no one!"

I followed him to the living room, still half-asleep, and was greeted by the sight of a small mountain of books piled on the coffee table.

"What's this?" I asked warily.

"Your first lesson," he said, smirking as he gestured to the stack. "Eight books. These will teach you more than a thousand training sessions ever could."

I groaned. "I thought you were going to teach me how to fight—you know, punching, kicking, the works?"

"I am teaching you to fight," he said, his smirk widening. "But brute strength alone won't save you in the supernatural world. Strategy, knowledge, and discipline—that's where true power lies. These books are the foundation of your training. Until you finish them, no physical lessons."

I gawked at him. "You're kidding, right?"

"Do I look like I'm kidding?" His tone was sharp, and I had to admit, he had a point.

Sighing in defeat, I glanced at the titles. The Art of War by Sun Tzu. Supernatural Weaknesses and Strengths. Tactical Deception in Combat. Even one that looked suspiciously like a beginner's guide to magical theory.

"This is going to take weeks," I muttered, eyeing the stack.

"Good," he said, crossing his arms. "Take your time. What matters is that you understand the material. And don't even think about skimming—I'll be quizzing you."

Reluctantly, I picked up The Art of War first. It was the shortest one, and I figured it'd be the easiest to get through. To my surprise, the lessons were practical and straightforward. Sun Tzu didn't just talk about battle formations or troop movements—he delved into the psychology of war. Deception, timing, knowing your enemy—it wasn't just about strength; it was about winning.

By the time I finished, two hours had passed, and I was already reaching for the next book: Supernatural Weaknesses and Strengths.

This one was different. The cover alone made it feel ancient, with faded lettering and worn edges. Opening it, I was immediately greeted by a detailed section on devils.

It outlined their strengths—everything from their near-limitless magical potential to their ability to fly. Bloodlines were a major focus, with specific notes on clans like the Bael and Gremory. The Power of Destruction caught my attention. It was a unique ability exclusive to certain bloodlines, capable of erasing almost anything it touched.

"Wish I had that," I muttered.

The old man's voice startled me. "Ah, yes. The current leader of the underworld—Sirzechs Lucifer—uses that power. He's said to be one of the top ten beings in existence."

I frowned. "What would it even feel like, standing face-to-face with someone like that?"

"Crushing," he said simply.

I moved on, flipping through sections on other supernatural species. Angels had their light-based powers, but they were surprisingly limited in number. Fallen angels, on the other hand, had more flexibility but lacked the pure strength of their angelic counterparts. Vampires were fascinating, with their regenerative abilities and blood-based magic. The book even detailed their weaknesses: sunlight, silver, and certain forms of holy magic.

Then there were youkai—foxes in particular. The chapter on senjutsu was a game-changer. It described how they manipulated natural energy, blending it with their own to enhance their physical and spiritual abilities.

"This stuff is insane," I muttered, rubbing my temples.

"Good," the old man said from the doorway. "The more insane it seems, the more respect you'll have for your opponents."

Eventually, I stumbled into the kitchen, my head pounding from all the information.

"Seems you're doing well," the old man said, stirring a pot on the stove. The aroma of stew filled the air, making my stomach growl.

"Just in time for dinner," he said cheerfully, setting the table.

I sat down eagerly, only to blink in confusion as he placed a plate of cold chicken, plain rice, and steamed broccoli in front of me.

"What's this?" I asked.

"Your meal," he said, digging into his own steaming bowl of stew.

"But why do you get the good stuff?"

He leaned back, fixing me with a serious look. "This is a lesson, Oscar. The world isn't fair, and you shouldn't expect luxury. That 'plain' meal is a blessing compared to what others get. Consider it training for the day when this might be all you have."

I stared at the plate, then at him, then back at the plate. With a sigh, I dug in.

The rice was dry, the chicken was cold, and the broccoli was… well, broccoli. I ate in silence, forcing each bite down as the old man worked through his second helping of stew, clearly enjoying himself.

"I hate this," I muttered under my breath, shoving a forkful of rice into my mouth.

"Good," he said with a grin that showed far too many teeth for my liking. "That means you're learning."

I shot him a glare, but he didn't seem to notice—or care. He leaned back in his chair, wiping his mouth with the back of his hand, and watched me with an unreadable expression.

"Listen, Oscar," he said, his voice dropping to a rare seriousness. "You're at the bottom of the ladder right now. Weak. Ignorant. Naïve. If you don't learn to endure the little struggles—like a bland meal—how are you going to face the real battles out there? You think devils, vampires, and fallen angels are going to go easy on you just because you're uncomfortable? This," he gestured to my plate, "is the least of your problems."

I wanted to snap back, to tell him how ridiculous it was to equate a bad meal to supernatural battles, but the words caught in my throat. Deep down, I knew he was right.

I finished my plate in silence, swallowing the last bite of dry chicken with a grimace.

"Not bad," he said, nodding approvingly as I set my fork down. "You didn't complain too much. Maybe there's hope for you yet."

"Gee, thanks," I said flatly, standing to rinse my plate in the sink.

The old man chuckled, pushing his chair back with a loud scrape. "That's enough for today. You've got a lot of reading to do tomorrow, so get some rest while you can."

He started toward his room, but paused in the doorway, glancing back at me.

"And Oscar," he added, his tone softer than before, "remember—every challenge, no matter how small, is preparing you for what's to come. If you can't master the basics, you'll never survive the real trials."

His words lingered in the air as he disappeared down the hall.