From MangaHelpers:
Mirai is the top soapland hostess (a specific kind of prostitute) in modern day Yoshiwara. One day, after being drugged by an angry rival, she seems to fall into a time-slip! She finds herself in a brothel of Edo period Yoshiwara, where she is accepted as a sex worker. Mirai quickly uses her modern-day techniques to rise in popularity to the top of the prostitutes. She makes friends with a girl named Ume, and makes a bitter enemy in the reigning top lady, Maiyuki. Mirai copes quite well as an Edo period prostitute, but will she ever find a way to return to her own time?