Star Trek's Mr. Sulu (George Takei) remains one of the franchise's most popular and enduring characters, with an extensive history explored over the years. First introduced in Star Trek: The Original Series, Sulu is mainly remembered as the helmsman of the USS Enterprise under the command of Captain James T. Kirk (William Shatner). Although he acted as a supporting character during TOS, Sulu was integral to the show's main cast, specifically because of his role as a bridge officer on the Enterprise which often put him in the thick of the action during an episode's main storyline.
https://screenrant.com/star-trek-sulu-tos-movies-history-explained/