Bleach: The Fifth Division Captain

Seiya knelt on one knee, silently gazing at the spot behind him.

There, half-buried in a pile of dirt, lay a fist-sized rock—the same one Tōsen had just thrown during his "surprise attack."

No spiritual pressure. No killing intent.

Just an ordinary rock, hurled with enough force to make a sound as it cut through the air…

And yet, that simple, insignificant object had shattered the carefully constructed world Seiya had built through his Zanpakutō's ability.

This was the flaw in Seiya's power.

"Seiya-kun, your ability is… too focused."

Aizen's calm voice carried a hint of reproach, though there was no malice behind his words.

Indeed, the essence of Seiya's power—the Ouroboros—lay in its predictive capabilities. His Zanpakutō created a Möbius loop, a maze of possibilities, based on the current state of both parties in battle.

In essence, it functioned like a highly precise simulation.

However, that very precision was also its greatest weakness.

The simulated world Seiya built was incredibly fragile.

While it wasn't so weak that a slight breeze could unravel it, any significant interference from an external source would throw it completely off track.

Aizen had proven that with Tōsen's simple act of throwing a rock.

Seiya knew this all too well.

But the root of the issue wasn't the power itself—it was Seiya's lack of spiritual pressure.

Had his spiritual energy been stronger, he could have expanded the parameters of his predictions to account for more variables: additional opponents, environmental factors, even unforeseen interruptions.

Theoretically, Seiya's power could simulate an entire world, predicting the movements of countless variables across a vast battlefield.

But for now?

Three seconds ahead and only between himself and a single opponent.

Any more than that, and he'd burn through his spiritual pressure in an instant.

Seiya chuckled bitterly to himself.

Predicting the world's future? Right… Maybe in my dreams.

Aizen slowly approached as Seiya coughed and sheathed his Zanpakutō.

"There's another obvious weakness, Seiya-kun," Aizen said, his tone almost casual.

"Your ability consumes far too much spiritual pressure."

"Even though you've already reached the level of a fifth-class reiatsu—impressive for a student—that's still not enough to sustain your power."

"Two uses… and you're already showing signs of exhaustion."

Aizen gently tapped his chin, lost in thought.

"If this isn't an issue with your personal reserves, then it must be the nature of your Zanpakutō itself."

And if that's the case…

"Seiya-kun, you need to change your strategy."

Seiya sighed, wiping the sweat and dirt from his face.

Aizen continued his lecture, his analytical mind dissecting Seiya's power with surgical precision.

"This ability of yours—it shouldn't be used at the start of a battle. It's a trump card, something to be deployed during a stalemate or critical moment."

"Unless you can drastically reduce its spiritual energy consumption, you should focus on conservative combat and hold back your power until the time is right."

Seiya couldn't help but marvel at Aizen's thorough analysis.

The man had only just witnessed Ouroboros in action, and yet he had already broken down its strengths and weaknesses with pinpoint accuracy.

This was Aizen's true strength.

His keen insight, his ability to peel back the layers of any mystery and lay bare the truth.

Aizen smiled faintly, his expression warm but measured.

"Let's continue."

"Your ability has some clear limitations," Aizen went on.

"For one, it's not suited for group battles. It's far more effective in one-on-one combat."

"And as long as the environment is controlled, and you've gathered enough information about your opponent, your Zanpakutō will allow you to dominate."

Hearing this, Tōsen nodded in agreement.

"A highly specialized power for single combat…" he murmured. "That's rare."

Despite his usual reserved nature, Tōsen couldn't help but offer a sharp observation.

Aizen chuckled.

"Yes, rare indeed. But…"

His expression shifted, and his eyes gleamed with an intense light.

"Seiya-kun, your ability is perfect for narrow paths."

"When two warriors meet head-on, with no room for retreat or reinforcements—you are the one who will always come out on top."

"You are a lone wolf, born to fight one-on-one battles to the bitter end."

"That's magnificent… far beyond my initial expectations."

Aizen's praise wasn't empty. His tone was filled with genuine admiration.

"You have a unique gift, Seiya-kun. Truly, you are worthy of being called my student."

Seiya sighed.

He wasn't surprised by Aizen's assessment.

Instead, he was in awe of Aizen's ability to unravel complex truths so effortlessly.

One battle was all it took for Aizen to fully grasp Seiya's strengths and weaknesses.

Not only that—Aizen had given him an exact combat role that fit his abilities perfectly.

A lone warrior. A duelist.

Until his spiritual power grew significantly, Seiya's best chance of victory lay in one-on-one duels, in environments free from outside interference.

"Am I really going to be able to keep up with someone like him?" Seiya wondered quietly.

Aizen's analytical prowess, his overwhelming presence—the gap felt insurmountable.

Still, Seiya didn't have time to wallow in doubt.

Aizen extended his hand, his expression as calm as ever.

"That's enough for today," he said kindly.

"Get some rest, Seiya-kun. Don't let any of this weigh too heavily on your mind tomorrow."

Seiya nodded, sighing again as he accepted Aizen's hand and pulled himself to his feet.

Three days later.

When the group gathered again, Seiya noticed something off about Aizen's demeanor.

The usual composure was there, but… his brow was furrowed, his expression tense.

"Is something wrong, Aizen-sama?" Seiya asked.

Aizen didn't hesitate to explain his predicament.

"The Hōgyoku… it's not progressing."

Despite absorbing the souls of over three hundred individuals—including ninety-eight registered Shinigami and more than a hundred spiritually gifted Rukongai citizens—

The Hōgyoku remained dormant.

"That's strange," Seiya said.

Aizen nodded.

"Yes. Even a Hollow would evolve after consuming that many souls… Yet the Hōgyoku shows no signs of change."

For the first time, Aizen seemed genuinely puzzled.

Seiya didn't comment further.

But in his mind, he recalled something important from the future.

The Hōgyoku's evolution didn't rely solely on quantity.

It required something far more unique.

Two souls, bound by fate.

"Those two… when will they show up?" Seiya thought quietly.

Time passed slowly.

A month went by.

Seiya continued to train with Aizen and Tōsen, honing his skills, sharpening his instincts.

And then, one day, during a routine excursion to Rukongai…

Seiya spotted a familiar face.

Someone he'd been waiting to meet.

At last.

The "key" to awakening the Hōgyoku had appeared.