Shogun and His Mistress 2 (1967)

In the year 1786, Shogun Ieharu Tokugawa selected beautiful Ochisa to be his concubine. It causes other concubines to become very jealous and mean. When the Shogun passes away, his concubines are forced to become nuns, which they are not happy to be. The subject is life inside a shogun's harem, and the treatment is again more restrained than in most of the historical pinku eiga films being produced by independents at the time, but the tone of this middle installment in the trilogy is decidedly more grim than that of its predecessor. There's a good deal of abuse and violence on display, as the shogun dies and his concubines are sent to a remote convent to become buddhist nuns. the hysterical nuns are being punished for their transgressions and committing suicide in grand exploitation fashion.

Unfortunately the movie Shogun and His Mistress 2 is not yet available on HBO Max.