What is the theme in Memoirs of a Geisha by Arthur Golden?

The term ‘danna’ usually means husband, but to a geisha, a danna is seldom used that way. A danna is more like a benefactor with benefits. Geishas of any standing never give themselves to a man without careful consideration and compensation. If the correct sort of man is interested in becoming a danna to a particular geisha and is willing to negotiate terms, most geishas are happy to enter into such an arrangement.