noun
protagonist; main character; hero or heroine
The central character in a novel, film, game, manga, play, or story. 英語の 'hero' can mean either a male hero or simply the central character; 主人公 itself is not gender-specific.
この小説の主人公は十歳の少女だ。
The protagonist of this novel is a ten-year-old girl.
The film depicts the main character's growth.
noun
head of a household; proprietor
Respectful use for the master or head of a household, or the proprietor of a shop. This sense is uncommon in modern everyday Japanese and can be confused with the much more common 'protagonist' meaning; ご主人, 主人, or 店主 are often used instead depending on context.
See also: 主人
古い用法では、主人公が家や店の主人を敬って指すことがある。
In older usage, 主人公 can respectfully refer to the head of a household or the proprietor of a shop.