This is a remake of the 1967 film Belle de Jour.
Drama series title "Hirugao" is derived from a relatively new Japanese expression "Heijitsu Hirugao Tsuma" which refers to housewives having afternoon affairs while their husband's are working. The expression "Heijitsu Hirugao Tsuma" is derived from the French film "Belle de Jour" which is itself based on the 1928 novel "Belle de Jour " by Joseph Kessel.