Toshio Koumura is a language teacher at Tomoya's school and 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. 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 is 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 meet. He retires one year later, prior to the end of the school segment of the story. In After Story, he returns and organizes the fake graduating ceremony intended for Nagisa, arranged by Tomoya.
Sugisaka is a member of the chorus club. She tries to force Nagisa to give up on establishing theatre club by threatening her, but later confronts Nagisa directly, telling Rie's past, hoping she will not bother Rie's dream. Youhei does not trust Sugisaka due to her usage of threat letter, and her attempt on messing up Nagisa's shoe cabinet. In the After Story anime, Sugisaka works as a waitress in the same family restaurant as Nagisa.
He has no name and but narrates the situation in the illusionary world seen through Tomoya's dream while referring to himself only as, "Me." He has his body created by the girl out of garbage so that he can be with her. The body is about half the girl's height. He can't talk as he is created without a mouth, so relies on body language to communicate with the girl. Unlike most characters in the series, he is created via CGI. (Source: Wikipedia) In ~After Story~, It is revealed that the Garbage Doll is Tomoya in a world after Ushio's death, as well as the girl being his daughter, Ushio. The last we get to see of the Garbage Doll and the girl is when the Imaginary World is supposedly destroyed.
The only human in the illusionary world, a world Tomoya dreams of. She creates a body out of garbage for an unnamed entity only referred to as, "Me," so that she will not be alone in the illusionary world. She is not created by CGI, everything she does is hand-drawn. (Source: Wikipedia) ~After Story~ It is revealed that the girl is Ushio, Tomoya's daughter in a world with her father after she dies in the real world.
Nishina Rie has played the violin since she was young, she entered a lot of concerts, and had won many competitions. Rie was set to go study overseas, but she was then involved in an accident that weakened her grip and prevented her from playing the violin as well as she used to. Rie was lonely when she entered this school, she almost gave up her life when Koumura confronts her and teaches her chorus. Thus, Rie regained her meaning of her life, and wants to create the choir club. In Kotomi's path, she lends Kotomi a violin, after Kotomi hears the violin from her. In the After Story, Rie works as a waitress in the same family restaurant as Nagisa.
YÅ« only appears in Yukine's path. Wanting to locate his sister, who is a delinquent, he meets up with Yukine. His mother escorts him later, leaving bad remarks on Tomoya, Youhei and Yukine.