Horny Working Girl: From 5 to 9(1982)

Overview:

A woman named Chieko Kuwano is hired as an assistant manager at a large corporate office in Japan. She’s smart, sexy, and willing to do almost anything for her sex-starved new boss but, since he’s married, his deviant behavior makes her uncomfortable. Fed up with the boss and his perverted ways, the ladies in the building band together to enact their own special kind of revenge… that is, after they have a lesbian three-way slumber party, of course!