Onepiece: I'm Aizen Sosuke

Zephyr stood before the group, his voice commanding yet composed.

"Observation Haki: the ability to strongly sense the opponent's 'voice.' When mastered, you can perceive the position and number of enemies beyond your line of sight and even predict their next move. However, it requires a calm mind. If you lose control of your emotions, this ability becomes unusable."

The students listened attentively, their expressions a mix of intrigue and determination. Zephyr then raised his hand, signaling the next demonstration.

"Now, let me show you Armament Haki."

As he spoke, his arm turned pitch black, coated with a hardened gleam. He casually picked up a nearby blade and crushed it effortlessly between his fingers.

"This is Armament Haki. It enhances both offense and defense. Watch closely."

The display left most of the students awestruck, their eyes wide in amazement. However, Aizen remained calm, his expression unreadable.

Inwardly, Aizen had little interest in mastering Armament Haki to its fullest potential. While undeniably powerful, it paled compared to his mastery of Reiatsu. With Kidō at his disposal, even Logia users—normally immune to physical attacks—were no threat. To him, pursuing Armament Haki was unnecessary.

Zephyr turned toward Sakazuki. "You're up. Attack me with everything you've got. Don't hold back until I tell you to stop."

"Understood!" Sakazuki replied, his voice filled with resolve.

He stepped forward, magma seeping from his arms as he launched a fiery punch at Zephyr. Yet, Zephyr evaded with ease, his movements seemingly effortless.

Sakazuki pressed on, his attacks growing faster and more ferocious, but none landed. Zephyr's Observation Haki enabled him to anticipate every strike. It wasn't long before the gap in their abilities became evident.

"Observation Haki..." Aizen mused, watching intently.

For him, this ability held significant potential. The power to predict and perceive an opponent's every move was invaluable, particularly in combat against unpredictable foes. It was a skill worth honing, even for someone of his caliber.

Once Sakazuki exhausted his attempts, Zephyr addressed the group. "Form pairs. One person will close their eyes and rely solely on their instincts to avoid their partner's attacks. This exercise is the foundation of Observation Haki. Aizen, you'll practice with me."

The students exchanged glances but refrained from objecting. Aizen's earlier displays of power had already earned him a level of respect, if not awe.

Aizen stepped forward, his movements deliberate yet relaxed. Sitting cross-legged, he closed his eyes, his breathing steady.

Zephyr approached, his voice carrying a tone of warning. "Aizen, you may be ahead of the others now, but don't let it get to your head. Mastering Haki is no easy feat. It requires patience and perseverance."

Aizen offered a faint smile but said nothing.

Without further delay, Zephyr raised his staff and aimed a strike at Aizen's head. To his surprise, Aizen leaned slightly to the side, evading the blow.

Zephyr frowned, attributing it to luck. He swung again, faster this time. Once more, Aizen dodged effortlessly.

Strike after strike, Zephyr increased his speed and unpredictability, yet Aizen evaded each attempt with the same calm precision.

"Impossible..." Zephyr muttered under his breath.

Finally, he stopped, his expression a mix of astonishment and curiosity. "Aizen, try using Armament Haki."

Aizen opened his eyes, frowning slightly. He looked at his arm, then complied. A faint, shimmering layer of Armament Haki covered his fist.

Zephyr's eyes widened. "As I thought... A natural genius."

Despite himself, Aizen couldn't help but reflect. *Armament Haki... It's powerful, but pales in comparison to Reiatsu. Still, mastering it could prove useful.*

Zephyr, meanwhile, felt his admiration for Aizen deepen. "This level of talent... He's no ordinary prodigy. If nurtured, he could surpass even the strongest of us."

Unbeknownst to the others, Zephyr's mind was already racing with plans to further Aizen's training. In his eyes, this young man had the potential to reshape the future of the Marines.