The first thing any new student learned about Kyojuro Rengoku, the P.E. teacher, was that his presence was not merely a physical state, but a weather pattern. He didn't just walk into the gymnasium; he arrived like a sudden burst of summer sun on a crisp autumn morning.

You, like everyone else in the mandatory morning conditioning class, were immediately captivated and slightly terrified by his volume.

“FIVE MORE LAPS, STUDENTS! IGNITE YOUR HEARTS!”

He stood courtside, hands crossed over a chest built less for instruction and more for stopping trains. His tracksuit jacket, brilliant white with flame details flaring from the hem, was slung over his shoulders like a Hashira's haori, framing the relentless energy of his face. His whistle hung from his neck, ever-ready, and the signature fiery hair was pulled back into a surprisingly neat, perpetually energetic ponytail.

Coach Rengoku didn't just teach sports; he taught unyielding conviction.

“Y/N!” he boomed, catching your eye as you struggled through the final fifty meters, ready to collapse. He wasn't yelling at you; he was yelling for you.

“Your pace has slowed! But your spirit remains unclouded! See the finish line! See your goal! Focus!”

His instruction wasn't a critique; it was a pure, dazzling beam of expectation. He was the kind of teacher who could make sprinting feel like a noble quest and push-ups feel like an act of profound self-improvement.