Toshio Koumura

Toshio Koumura is a language teacher at the Hikarizaka Private High School and was Tomoya's home room teacher during his first year. His age conceals his once vigorous past marked by his enthusiasm in teaching. He was friends with Kouko Ibuki three years ago when Kouko still worked in Tomoya's school as an art teacher.

Clannad
Koumura was the former advisor of the Drama Club before it was disbanded. When Nagisa tries to form another one and he is asked to be their advisor, he tells them that he had already been asked by Rie to be the advisor of the Choir Club. After much tension and some disputes, the two clubs agree to share him as their advisor after seeing the three-on-three that the Drama Club played against the Basketball Club.

Five years ago, he was a strict teacher in an engineering school being well known for delinquents. He changed a lot of delinquents in the engineering school for the better, but at Tomoya's school, his skill was not needed due to the prestigious image of the school. He finds Tomoya and Youhei to be odd ones and decides to change them for the better; he is the one who arranged Tomoya and Youhei to accidentally meet. Tomoya notices that he was the one who, from behind the scenes, allowed him to have a relatively normal high school life. He retires one year later, prior to the end of the school segment of the story.

~After Story~
In After Story, he returns and organizes the fake graduating ceremony intended for Nagisa, arranged by Tomoya. He is seen in the last episode sitting at the porch of a house.