"The Iga heir," Haruka sneered, spinning a kunai between his fingers. "A boy playing dress-up. Do you think that suit makes you a ninja? You’re just a relic of a dying clan."
Ittoki looked down at his hands. They were trembling. "Is it always going to be like this? Just because our ancestors hated each other, we have to spend our lives trying to kill each other?"
It seems you are looking for a story inspired by of the English dub of Shinobi no Ittoki . In this episode, titled "Cycle of Fate," the tension between the Iga and Koga clans reaches a boiling point during the Ninja Academy exams. Shinobi no Ittoki (Dub) Episode 5
Here is a story expanding on the themes of that episode, focusing on the weight of heritage and the "cycle" that traps these young ninjas. The Weight of the Blade
The battle that followed was a blur of high-tech gadgetry and ancient martial arts. Haruka was faster, his movements honed by years of brutal Koga conditioning. But Ittoki had something the Koga lacked: a reason to live beyond the kill. He didn't want to conquer; he wanted to protect the small, quiet life he had left behind. "The Iga heir," Haruka sneered, spinning a kunai
Haruka hit the ground, gasping for air. Ittoki stood over him, his breathing ragged. He had the opening. He could have ended the cycle right there.
Kousetsu finally turned, her mask reflecting the dim light of the artificial moon. "It’s a cycle, Ittoki. A wheel that keeps turning. We are just the spokes." You’re just a relic of a dying clan
"You're hesitant, Ittoki," Kousetsu’s voice came from the shadows, cold and precise. She didn't look at him, her eyes fixed on the treeline where the Koga students—the 'elites'—were surely waiting. "In the world of shinobi, hesitation is a death sentence. The Koga don't care about your heart; they care about your head."