"I'm not going to kill you," Ittoki said, his voice steady for the first time. "Because if I do, someone else will come for me. And then someone will come for them. I’m done being a spoke in your wheel."

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.

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.

In a desperate maneuver, Ittoki used his suit’s exhaust to create a smoke screen, not to escape, but to close the distance. He didn't strike with a blade. Instead, he used a palm strike to the chest, a move his mother had taught him—not to kill, but to disarm.

The air in the Koga training grounds was thick with the scent of ozone and damp earth. Ittoki Sakuraba stood at the edge of the simulated forest, his lungs burning. He wasn't just fighting his classmates anymore; he was fighting the shadow of a father he never truly knew and a future he never asked for.

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.