Akasen (赤線) was the Japanese slang term for districts historically engaged in the sex work industry in Japan, specifically within the time period of January 1946 through to March 1958.

The Recreation and Amusement Association or RAA, was the largest of the organizations established by Japanese authorities to provide organized prostitution to prevent rapes and sexual violence by Allied occupation troops on the general population, and to create other leisure facilities for occupying Allied troops immediately following World War II. The RAA "recruited" 55,000 women and was short-lived.