Kouzou Etou

A piano teacher also known as the "Harisen teacher", because he always carries one during his class which uses to punish his students for their mistakes. He was Chiaki's teacher at the start of the story, until he was abandoned by him. One day he listened one of Nodame's performances and decided to become her teacher, even if refused by her. He eventually gives up his harisen in order to convince Nodame to take lessons from him.

(Source: Wikipedia)