Take Japanese Sengoku History and replace most of the important characters with female versions, add a protagonist from the future and voila.

The way the whole from the future aspect is done is actually very clever. Take for example how the protagonist becomes Toyotomi Hideyoshi.

Despite some of the obvious liberties done for the whole time travelling protagonist and the gender-swapped historical figures, the show stayed pretty true to the events that actually occurred (the results anyways). The resulting script is pretty clever in how it attempts to do this.

May very well be my top under the radar show of the season.