The Overpowered Old Mage Possessed the Body of the Golden Sun

The academy had one utterly useless bastard named Geum Taeyang.

"Back in my day, we all handled stuff like this. Kids these days don't even know how to fight properly with magic anymore."

Then one day, that bastard got way too strong.

The cover was made with Novel AI! If there's any issue, it's on the author!

Our academy has this one piece of trash named Geum Taeyang who's so useless it's disgusting.

"In my time, everyone could do at least this much. These days' youngsters don't even know how to fight using magic properly, tsk tsk."

Then one day, that son of a bitch suddenly became insanely strong.

The cover image was generated with Novel AI! Any problems with it are the author's responsibility!

In the heart of Seoul, where towering skyscrapers pierced the clouds and neon signs flickered alongside ancient magical wards, stood the prestigious Hero Academy. It was a ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠place where the children of the world's most powerful families trained to become the next generation of heroes, mages, and warriors. Magic engineering blended seamlessly with cutting-edge technology—smartphones could cast ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠simple spells, flying cars navigated enchanted airspace, and augmented reality glasses displayed real-time battle stats.

But not everyone at the academy was a prodigy.

Geum Taeyang was the academy's resident failure. A third-year student from a once-noble but now declining family, he had zero talent for magic, abysmal grades, and an even worse attitude. Most days he spent lounging in the back of the classroom, muttering complaints about "kids these days" while everyone else practiced their spells and combat forms.

"Ugh, this is so annoying," Taeyang grumbled, slouched over his desk as the magic engineering professor droned on about mana circuit optimization. His golden hair—once the pride of his family lineage—looked messy and unkempt, and his uniform was wrinkled like he'd slept in it. Which he probably had.

The girl sitting in front of him, a sharp-eyed beauty named Han Seoyeon, shot him a glare over her shoulder. "Can you shut up for once? Some of us are actually trying to learn."

Taeyang snorted. "Learn? What's the point? Back in my day—"

"Your day? You're twenty, you idiot," Seoyeon snapped, her voice dripping with irritation. She was the top student in their year, captain of the magic dueling club, and had already received offers from three major guilds. Everything Taeyang wasn't.

He just grinned lazily. "You wouldn't understand. When I was your age..."

The entire class groaned in unison. This was a daily occurrence. Geum Taeyang and his endless nostalgic rambling. No one knew why he talked like an old man trapped in a young body. Some said it was brain damage from a childhood mana explosion. Others figured he was just trolling everyone for attention.

Only Taeyang himself knew the truth.

These brats. If only they knew who was really inside this useless shell.

Because Geum Taeyang wasn't actually Geum Taeyang.

Deep inside that disappointing body lived the soul of Archmage Karsus, one of the most powerful mages in history. A legendary figure from five hundred years ago who had dominated battlefields, toppled empires, and mastered magic so advanced it bordered on godhood. Karsus had been on the verge of achieving true immortality when a betrayal from his closest disciple sent his soul hurtling through time and space.

And somehow, it had ended up possessing the body of this pathetic academy dropout.

I spent the first few months thinking this was some kind of hellish punishment. No mana affinity, a broken magic core, and a reputation lower than a goblin's ballsack. But now...

Taeyang—or rather, Karsus—smirked to himself as he felt the immense power stirring within. After months of secretly reconstructing his ancient knowledge within this modern body, he had finally succeeded. The old mage's genius had overcome the limitations of his new vessel. Mana flowed through him like an unstoppable river. Ancient spells that should have been impossible in this era were now at his fingertips.

He was overpowered. Ridiculously so.

"Hey, Taeyang!" A loud voice boomed from the classroom entrance. It was Kang Doohyun, the academy's top combat specialist and self-proclaimed rival to anyone with a pulse. "You still hiding in here like a coward? The practical exam is about to start. Or are you gonna skip it again and cry about 'how things were better in the old days'?"

The class snickered. Doohyun was built like a tank, with muscles that strained against his uniform and a face that looked like it had been chiseled from marble. He was everything Taeyang was supposed to be—talented, popular, and aggressively competitive.

Taeyang slowly stood up, cracking his neck with a series of loud pops. The lazy, good-for-nothing look in his eyes was gone. In its place was something ancient. Something terrifying.

"Practical exam, huh?" he said, his voice suddenly carrying a weight that made the entire room fall silent. "Fine. Let's do it."

Seoyeon blinked in surprise. Doohyun raised an eyebrow.

"Wait, you're actually participating? For real this time?" Doohyun asked, crossing his arms. "Don't embarrass yourself too badly, golden boy. I'd hate to have to carry your sorry ass out of the arena again."

Taeyang smiled. It wasn't his usual sloppy grin. This smile was sharp, confident, and carried five centuries of overwhelming arrogance.

"Carry me?" he chuckled. "Kid, you couldn't carry my jockstrap."

The entire class gasped. Even the professor dropped his tablet.

Doohyun's face turned red with rage. "You little—! That's it. I'm gonna enjoy wiping the floor with you in front of everyone."

As the two of them headed toward the academy's massive combat arena, whispers spread like wildfire across the campus. Students pulled out their phones. Group chats exploded. The academy's official forum lit up with notifications.

Inside the arena, thousands of seats were already filling up. Holographic screens floated above the combat zone, displaying real-time analytics. The headmaster, an elderly mage with a long white beard that somehow incorporated fiber-optic lighting, sat in the VIP box looking mildly interested for the first time in years.

"Geum Taeyang versus Kang Doohyun," the announcer's voice boomed through the speakers. "Begin!"

Doohyun didn't waste time. He activated his signature skill immediately, his body glowing with crimson aura as he charged forward like a human battering ram. "Crushing Tiger Fist!"

The ground cracked beneath Doohyun's feet as he closed the distance in a blink. His fist cut through the air with enough force to shatter reinforced concrete.

Taeyang didn't move. He simply raised one hand.

"Absolute Barrier: Ninth Circle Edition."

A translucent golden shield materialized around him. Doohyun's devastating punch slammed into it—and stopped dead. The impact created a shockwave ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠that blasted dust across the entire arena, but the barrier didn't even flicker.

The audience fell into stunned silence.

Doohyun staggered back, eyes wide. "What the... that's impossible! Your mana rating is F-rank! How—"

Taeyang lowered his hand, the barrier dissolving into sparkling motes of light. His eyes glowed with an otherworldly golden hue—the same color as the sun itself.

"Like I said," he spoke softly, but his voice carried to every corner of the massive stadium thanks to a casual amplification spell. "You kids these days don't know how to fight with magic."

He took one step forward.

The entire arena trembled.

"Let me show you how it's done."

And just like that, the useless golden boy of Hero Academy stopped being useless.

The old monster inside him had finally woken up.