Tail of the Moon: The Other Hanzo(u)(2002)

Tsuki no Toiki: Ai no Kizu

Kaguya doesn't remember who she is or why she has a huge scar on her back. Six months ago, she was found injured and unconscious in a field of bamboo. Now she works as a housekeeper and babysitter at a brothel, living her new life simply as "Kaguya."

Kaguya's real identity is entwined with two men--Hanzou, a handsome bodyguard of Okazaki Castle, and Hanzo, a leader of the ninja village of Iga. Between amnesia and mistaken identity, no one knows for sure what kind of person Kaguya is. Only her distinctive scar will lead her to the truth...

(Source: VIZ Media)