From Sweet Indulgent:

Hana is a normal teenager who goes to school normally, that is until she gets run over by a car... or did she? Suddenly, she finds herself in a weird place known as the "Red Light District"... in EDO PERIOD?! Trying to find a way to get back to her own time, she somehow gets mistaken for a prostitute and has to escape. Not expecting to be saved by a gentleman, she suddenly ends up in a geisha house.. but then she is bought by the same guy who helped her earlier?!