Toshio Koumura teaches language arts and serves as Tomoya's homeroom teacher during first year. He's older now, but his past reveals someone genuinely passionate about reaching troubled students. Three years before the story, he and Kouko Ibuki were close friends.
His real reputation comes from five years back, when he worked at an engineering school notorious for delinquents. He was tough, direct, and effective—actually turning kids around who everyone else had written off. That skill became his identity. When he transferred to Tomoya's prestigious school, though, there wasn't much use for a delinquent reformer. The place didn't have that problem. So Koumura spotted Tomoya and Youhei as the closest thing to "projects" available and made it his business to straighten them out. He's actually the reason those two became friends in the first place.
He doesn't stay at the school long. He retires partway through the main story, before things wrap up. Later, in After Story, he comes back into the picture to help Tomoya pull off a fake graduation ceremony for Nagisa.
Content compiled by AnimeList.moe from publicly available sources.
