The Koyama Clan, once a powerful and isolated clan outside the Hidden Leaf Village, was known only as an expendable force to be used in war. To the village, they were but a tool, valued far less than the prestigious Uchiha Clan. The Uchihas, with their unique Sharingan, were seen as superior.

Understanding this harsh reality, the leader of the Koyama Clan, Teiyu Koyama, decided to keep the true abilities of their rare ice-blue eyes, known as the Seigan, a closely guarded secret. He only disclosed to the Hokage that the Seigan transformed its bearers into ruthless combatants, enhancing their speed, strength, and chakra. What Teiyu withheld was that the Seigan also granted advanced sensory perception and the ability to manipulate water and ice chakra with deadly precision.

Yet, not all members of the Koyama Clan possessed these eyes. Most were born with normal blue eyes, especially among women. The chances of a female inheriting the Seigan were as rare as one in five. But those who did would undergo rigorous training, rivaling that of the strongest warriors.

One such exceptional talent was Erza Koyama—a rare gem among her kin.

"Erza!"

The young girl awoke abruptly to her mother's voice. Quickly, she donned her black haori, embroidered with blue roses, and hurried to grab breakfast.

"Good morning, Mother." Erza greeted politely, noticing the tension in Hina Koyama's demeanor. "What's wrong? You look worried."

Her mother turned, eyes clouded with concern. Resting a hand on Erza's shoulder, she knelt down.

"Did you forget what today is, dear? It's your first day at the Ninja Academy! From now on, you won't be training with our clan warriors. Instead, you'll focus on becoming a proper Leaf Village ninja," Hina explained.

"Become a ninja?" Erza echoed, frowning. "But Father said I'd become an assassin no matter what."

"That's…" Hina hesitated, sighing softly. "Your father agreed to let you choose your path after you graduate. You're the first Koyama to attend the Academy—an honor no one else has. That makes you special, Erza."

Erza simply nodded, absorbing her mother's words. Following her down a worn path through the village, she stole a glance at the clan members training relentlessly. Questions swirled in her mind, but she chose to stay silent, sensing her mother's pride and excitement.

As they walked through the Leaf Village, Erza felt the weight of curious stares. Their icy blue eyes marked them as outsiders. Most villagers knew little about the Koyama Clan, but those who did understood the chilling aura they emanated.

Finally, they arrived at the Ninja Academy—a place where aspiring shinobi were molded. But Erza didn't want to be a shinobi. She wanted to follow in her father's footsteps as a feared assassin.

After bidding her mother goodbye, she entered the bustling academy halls. Children scrambled to find their classrooms, chattering excitedly. Her own class was just around the corner.

Standing before the door, Erza sensed the distinct chakra signatures inside. With a deep breath, she pushed it open and stepped into a new chapter of her life.

"Oh! There you are!"

The teacher, already in the midst of taking attendance, looked up. She gave a quick, respectful bow.

"Apologies for being late, sensei. I'm Erza Koyama."

"Haha, no worries!" The man grinned warmly. "I'm Iruka-sensei. Go ahead and take a seat in the far-right corner. We're about to assign teams."

She nodded and moved to her seat, subtly scanning her classmates. A spiky-haired blonde boy caught her attention, sitting beside a brooding dark-haired boy.

'So that's the Nine-Tails Jinchūriki and the Uchiha,' Erza mused. There was nothing noteworthy about the blonde other than the powerful beast sealed within him. But the Uchiha… His older brother, Itachi, was already a legend in the village, his name spoken in hushed tones.

"Now, for the last few teams!" Iruka's voice snapped her out of her thoughts.

Startled, Erza realized she had been too lost in observation. Iruka continued:

"Sakura, Naruto, and Sasuke will be the last team! As for you, Erza, you'll be assigned a special mentor, since your abilities surpass those of your peers."

The announcement caused a ripple of murmurs among the students. Erza, unfazed, nodded in acknowledgment. From the moment she stepped into the classroom—no, even before that—she knew she was on a different level.

"Hey!" a voice called out.

Erza turned to see the blonde, Naruto, waving enthusiastically.

"What is it?" she asked coolly.

"Just you wait! I'm gonna become stronger than you and become the Hokage!" he declared confidently.

Erza merely blinked, dismissing his challenge. It would be a long time before he even came close to catching up. By then, she would be far beyond reach.

"Erza," Iruka called, "your mentor is waiting outside the Academy."

"Thank you, sensei."

Stepping outside, Erza felt a strange calm settle over the courtyard. A gentle breeze brushed against her skin, and she frowned, her instincts tingling.

Something's wrong. Without hesitation, she bit down on her finger, allowing a droplet of blood to drip. Instantly, the surreal sensation vanished. She'd broken free from the genjutsu.

"Well done. Your intuition is just as sharp as they say."

Erza's eyes widened. She turned to see a tall figure emerge from the shadows, wearing a black cloak.

"Itachi Uchiha."

"That's right."

A kunai flashed through the air. Erza reacted instantly, bending backward to dodge, but the kunai disappeared, replaced by Itachi himself, aiming a sweeping kick at her legs. She leaped back, executing a flawless flip, and landed in a defensive stance, scanning his movements.

"Hm, you're better than I was at your age," Itachi remarked, a faint smile on his lips.

"Why are you my mentor?" Erza asked bluntly, eyes narrowed. "Is it because of our eyes? The Seigan has abilities no other clan possesses."

"That's part of it," he conceded. "But it's also because I'm one of the few who can help you reach your true potential. After all, you and I both know how rare your talent is."

Erza considered his words, then nodded. "Understood. When do we begin?"

"I don't believe in wasting time," Itachi replied. "So how about right now?"

And with that, their training began—an unprecedented partnership between two of the most talented prodigies the village had ever seen.