Sensei

The unnamed Sensei (Japanese for teacher) (height: 5'6") is Nobita's teacher and the semi-quaternary antagonist of the Doraemon series. In the English dub he is known as Mr. S. In the Hindi dub, Sensei is simply referred to as Sir.

He is a strict teacher who often punishes Nobita for failing his tests, being late to school, or forgetting his homework. Many of his punishments range from standing in the hallway to sweeping the classroom after-school. The Sensei is often fooled by Suneo Honekawa's convincing acts of lying and is impressed with Hidetoshi Dekisugi's good grades. He often pays unexpected visits to the Nobi’s in order to inform Tamako about Nobita’s progress. The Sensei also usually sees Nobita on the streets and often encourages him to work and study harder.

His real name is unknown and he is only referred to as "Sensei", but in the 1973 anime, his name is given as Ganari (我成).