Everything I thought about this film (I still like it) was BLOWN away by this detailed explanation:
sukekomashi-gaijin - Spirited Away (千と千尋の神隠し）
Spirited Away (千と千尋の神隠し）
Much like Miyazaki's other work, Tonari no Totoro, a few dark theories have circled Sen to Chihiro no Kamikakushi, (Spirited Away in the West).
However, unlike the darker theories for Tonari no Totoro, which, while convinving, still leave a lot of room for doubt and counterarguments, Spirited Away's 都市伝説 toshi densetsu, urban legend is a lot more credible, even blatantly obvious.
Again, it is important to stress that none of this was discovered by me. The idea to look into this came from a comment on the Totoro page by an anonymous user. The facts are pulled from various Japanese websites and even Wikipedia. As always, if you don't want your opinion of this movie to change, then don't read on.
There's no easier way to say it than to say it, but Spirited Away is a story of prostitution.
In order to save her parents, who had been turned into pigs for eating food that wasn't theirs, Chihiro is forced to work in what is referred to as an 油屋 aburaya-ya, or oil house. In reality this is a portrayal of a 湯屋 yuya, an old type bath house (or hot water house).
Chihiro is forced to work as a 湯女 Yuna, and this word is used in the Japanese version. Despite the many (Japanese and abroad) reviews and articles written about Spirited Away, few touched on this interesting naming convention; Why is she called a Yuna?
Some dictionaries (Jim Breens, for example) will give an accurate definition of yuna - a yuna is a woman who services men at bath houses, which includes washing and sexual favours, and these were big business in the Edo period of Japan. In today's modern Japan, the bath houses of yesteryear have been replaced with the ソープランド, Soap Land, and the workers, the yuna, are now known as ソープ嬢 soopu jou.
As a direct result of the movies success and acclaim, the name Yuna suddenly became popular as a girl's given name. A lot of parents scurried to change their daughter's names upon learning what yuna meant.
The patrons we see were all men, as are the 'eight million' patrons in the movie (they are all 男神 otokogami, male deities).
Chihiro is hired by the manager of the oil house, 湯婆婆 Yubaba, and is forced to adopt another name, "Sen." In the Edo period red-light district, it was common practice for prostitutes to work using a different name, something of a 'stripper name.'
So why make a story about this? Well, apparently the idea came from the producer, Suzuki. He pitched the idea as: "How about a story about a girl who can't even greet people properly working in a cabaret club? It would be like training to open her heart," to which Miyazaki replied "That's it!"
When later asked in an interview about why he chose the particular story, Miyazaki is reported to have answered:
I think the most appropriate way to symbolize the modern world is the sex industry. Hasn't Japanese society become like the sex industry?
Yet another theory behind the movie's unusual plot is one involving kidnapping by North Korea, and being forced into a low-pay labour job, but there is not much in this theory to give it credit.
Also, this similar analysis of TOTORO:
sukekomashi-gaijin - Tonari No Totoro