In the first year of the Kan’ei era (1624), imagine Jubei Yagyū, the famed sword instructor to the Tokugawa clan, born as a woman. She has concealed her sex her entire life, until one day, Shogun Tokugawa Iemitsu accidentally sees her unclothed and demands her submission. Jubei refuses, sparking a ruthless pursuit. Forced to flee, she relies on the clandestine discipline known as the “Naked Sword” technique, rashinken, to survive.