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.
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
"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." Haruka hit the ground, gasping for air
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?" He could have ended the cycle right there
"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."
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.