The entire movie is a metaphor for prostitution
Spirited Away is a 2001 Japanese animated film that was written and produced by the great storyteller himself, Hayao Miyazaki. The film is about a young ten-year-old girl having to work in a bathhouse for an evil witch named Yubaba, because her parents had foolishly eaten food left out for the town's gods, and turned into pigs as a result of their gluttony. However, because of the film's main plot, a theory for this movie has exploded on the Internet. This is that theory.
According to the theory, the film is actually a metaphor for prostitution. Of course, there's no actual sex in it, since it is a children's film. However, the elements of this concept are still present in this movie. For example, when Chihiro, the film's lead character, is forced to work for the wicked Yubaba, she works as a yuna. A yuna is a Japanese word for a woman who works with bathers, or quite simply, bathhouse prostitutes. She's also given the name Sen, which was a common name given to female prostitutes during the Edo period.
However, this may be one of the few times in which a fan theory may actually hold water and might even be "true". When confronted with the question about why he made a movie like this, Miyazaki answers the question by saying that he thought the most appropriate way to depict Japanese society was through the sex industry, and he asked the interviewer himself a question on if Japanese society was becoming just like the sex industry. So, unlike the theories surrounding Totoro, this theory has been out right confirmed by the creator himself.
However, there seems to be no official word from Studio Ghibli on this matter, so it remains a theory.