In the alternate history of Japan’s Edo period, a devastating plague known as the redface pox sweeps the nation, fatally striking only young men and boys. With the male population reduced to a fraction of what it once was, the country’s social structure is turned upside down. Women become the primary laborers, heads of households, and political leaders, while men are treated as a precious, protected resource valued primarily for their ability to ensure the survival of family bloodlines. At the top of this new social order, the role of the Tokugawa shogun, the nation’s military ruler, is quietly inherited by a woman.

The story begins during the reign of the third shogun, Tokugawa Iemitsu. Unbeknownst to the public, the real Iemitsu, a young man, has already died from the red pox. To prevent the collapse of the Tokugawa dynasty, his powerful and calculating wet nurse, Kasuga no Tsubone, orchestrates an elaborate deception. She secretly brings a young girl, Chie, the late shogun’s illegitimate daughter, into Edo Castle. Raised as a boy and groomed to impersonate her father, Chie is forced to live as the female Shogun Iemitsu, a secret known only to a few within the inner chambers of the castle, the Ooku.

As the teenage shogun, Iemitsu is withdrawn and emotionally scarred, having been sexually assaulted by a guard in her youth, an event that resulted in a stillbirth. She keeps everyone at a distance, ruling with a cold and imperious demeanor. Desperate to secure an heir to continue the charade, Kasuga no Tsubone searches for a suitable consort. Her target is Arikoto, a handsome and virtuous monk of noble Kyoto lineage who has arrived in Edo. Using threats against his order, Kasuga forces Arikoto to abandon his vows and enter the Ooku as Iemitsu’s personal attendant and potential concubine, accompanied by his devoted young disciple, Gyokuei.

Arikoto initially resists his fate but is shocked to discover the shogun is a woman living under an unbearable burden. While Iemitsu is hostile, Arikoto’s innate kindness and non-judgmental nature begin to break down her defenses. Unlike everyone else who sees her as either a tool of the state or an object to be used, Arikoto affirms her worth as a woman, Chie. A deep and forbidden love blossoms between the former monk and the female shogun, giving Iemitsu the emotional strength to embrace her role as a leader.

However, their love is fraught with political necessity. Iemitsu must produce an heir, but it becomes clear that Arikoto is unable to father children. Following the death of the powerful Kasuga no Tsubone, Iemitsu reveals the truth of her gender to her lords, declaring herself the first openly female shogun. To secure the dynasty, she makes the agonizing decision to take other male concubines, including the loyal Gyokuei, to bear children. Arikoto, unable to be her husband in the traditional sense, becomes her most trusted advisor and the director of the Ooku, dedicating his life to supporting her rule.

The narrative arc follows Iemitsu’s journey from a traumatized pawn to a decisive and beloved ruler who legitimizes female succession, and Arikoto’s transformation from a reluctant prisoner to a man who finds purpose in sacrificing his future for the woman he loves. After Iemitsu’s death at the young age of twenty-seven, Arikoto remains in the Ooku to guide her successors. Their story of devotion and sacrifice sets the precedent for the future of the shogunate, establishing the Ooku not just as a private quarters, but as a formal institution of beautiful men serving the female shogun—a world of three thousand men that will endure for generations.