* 若様 (wakasama): This is probably the closest and most common translation. It's polite and traditionally used for a young man of high social standing, often the son of a wealthy family or a noble.
* 坊ちゃん (bōchan): This is a more informal and somewhat childish term for a young master. It implies a slightly spoiled or pampered young man. It's less formal than *wakasama*.
* 御曹司 (gosōji): This is a more formal and respectful term for the son of a wealthy or influential family. It emphasizes the family's status more than the young man's age.
The best choice depends on the specific situation and the desired level of formality. If you can provide more context (e.g., the story, the social setting), I can help you choose the most appropriate word.