Jigorou Kuwajima trained both Zenitsu and Kaigaku back when he was still an active Pillar in the Demon Killing Corps. He's mostly known through flashbacks in the manga—a short, elderly guy with grey hair and a prominent scar below his left eye, usually leaning on a wooden cane. He dressed in a simple jinbei-style kimono, not unlike what Sakonji Urokodai wore.
What stands out about him is his commitment to his students. Yeah, he was strict with training, but he genuinely cared about raising the next generation. Zenitsu has said that despite constantly whining and running away during his lessons, Jigorou never once gave up on him. He'd actually pulled Zenitsu out of debt and taken him under his wing, showing incredible patience—even just watching Zenitsu nail the first form made him happy.
His whole philosophy centered on perfecting techniques through repetition, treating it like the forging and purifying of a sword. That kind of methodical, almost spiritual approach to training defined him as a mentor.
Content compiled by AnimeList.moe from publicly available sources.
