Teacher is a very quiet and shy over looked member of the club, but is actually the teacher who is in charge of the club. Her real name has never been revealed. She said she's been teaching for 12 years, which should at least put her in her early thirty's.
Even though she has been has been a teacher at the academy for 12 years, she does not have her own class; she makes up for this by helping around the school. She is very clumsy and often ends up screwing up in anything she tries to do, which tends to make her cry. The other members hardly take notice of her, often forgetting she's even there, which also makes her cry.
Without her glasses on she is actually very beautiful and can be mistaken for someone else (as Densuke has done in the past.). Unfortunately she cannot see without her glasses.
Early in the manga she was the only realistically proportioned member of the club. Though her breasts are not the most prominent in the club, most of the ecchi scenes with her are about her butt. When her glasses are on you normally cannot see her eyes.
She can usually be seen with Komoe.
In the OAV she is voiced by Chiemi Ishimatsu in the japanese and Mari Devon in the english