In Ōoku: The Inner Chambers, when the third shogun dies, Lady Kasuga brings his illegitimate daughter to Edo Castle to take his place.
When the chief scribe, Master Murase, gives the eighth shogun “The Chronicle of the Dying Day” to help her understand the history of her country, he tells her that contrary to popular belief, the Honored Kasuga was not a man.
Furthermore, the third shogun was not born a woman; the title was held by a man first. “The Chronicle of the Dying Day” tells the eighth shogun the story of Lord Iemitsu, the third shogun.
The first female shogun
Before red-face smallpox changed everything, the society was patriarchal; it was men who inherited titles from their fathers, including the shogunate. Lord Iemitsu was the last male shogun.
Red-face smallpox only affected younger men, but in rare cases, it claimed the lives of older men as well. Lord Iemitsu is one of those rare cases. He dies at the age of thirty-one without a rightful heir.
The disease also kills the other men of the Tokugawa clan who could have taken his place. Fearing that provincial lords might try to seize power, Lady Kasuga, the third shogun’s wet nurse, decides to keep the shogun’s death a secret.
She orders the death of the doctor who treated the shogun, and the shogun’s body is said to be that of Lady Kasuga’s son, Masakatsu. Only a few trusted officials are informed about the shogun’s death.
Lady Kasuga knows that she cannot keep this secret for long and that she must get a male heir to take the shogun’s place in order to prevent war and chaos in the country. Her only hope of being able to do that is to get the third shogun’s illegitimate daughter to produce an heir.
The third shogun had raped a woman, who then gave birth to a daughter, but the shogun claimed that he did not know the woman. Lady Kasuga had arranged a wet nurse for the child, and the child lived with her mother and nurse on the outskirts of Edo.
This child is known as Princess Chie. After the third shogun’s death, Lady Kasuga gets Princess Chie’s mother and nurse killed and brings Princess Chie to Edo Castle to take her father’s place.
The title of Princess Chie is taken from her, and as a woman’s name cannot be listed in the family tree of the Tokugawa clan, she is given her father’s name and title — Lord Iemitsu. Additionally, she is made to dress like a man.
Her son is meant to be the next shogun, but even then, the male bloodline of the clan will be broken, so everything has to be done secretly. To hide the fact that the third shogun is now a woman, Masakatsu poses as the shogun from behind a screen.
With time, when the male population does not increase, Iemitsu begins to take charge and proves her worth as the shogun. She reveals her face to the public, and no one objects to the third shogun being a woman.
She claims that she is merely acting on her father’s behalf, and so she retains his name and title. In history, she is the one who is known as the third shogun, not her father.