The Ōoku —

A harem swirling with intense emotions.

The Ōoku is where beautiful and talented women are gathered from all across the land to bear the heir of His Majesty, the ruler. At the same time, it is an important place that plays a crucial bureaucratic function. Stepping into this unusual society with its own rules are young newcomers Asa (Tomoyo Kurosawa) and Kame (Aoi Yuki). Blessed with both intelligence and beauty, Asa aims to improve her standing, while Kame searches for a sense of belonging in this place she has always dreamed of. On the day of their induction, these two girls of opposite personalities are forced to participate in a ceremony to become part of the group by sacrificing their most cherished belongings to the Water Goddess, a deity worshiped within the Ōoku. As a result of this event, a bond forms between the two girls.

The elder Utayama (Mami Koyama) oversees the women while prioritizing the prosperity and continuation of the Ōoku, but she conceals something behind her stony facade. Slowly, over time, something uncanny begins to envelop the women. As their powerful emotions accumulate each night, the strange sound of a spinning paper umbrella echoes from the shadows and the maidservants begin to lose their minds, as though they are possessed.

Eventually, a pivotal tragedy occurs. The Medicine Seller (Hiroshi Kamiya) proceeds to the heart of the Ōoku, but he cannot draw the Sacred Sword to exorcise the mononoke unless he learns the being’s “Form,” “Truth” and “Reason.” When the Medicine Seller uncovers the frightening and heartbreaking truth hidden in the Ōoku, the ceremony of exorcism and redemption begins.

[Source: Netflix]

Shortly after the intense showdown in Mononoke the Movie: The Phantom in the Rain, the Medicine Seller appears once again in the inner chambers of the Ōoku. Within, dynamics are shifting in the wake of the previous incident. Otomo Botan, a woman from a distinguished family, succeeds Utayama as the new director and begins enforcing a strict leadership style rooted in discipline and balance. This creates growing tension between her and Fuki, a seasoned courtesan who once enjoyed the exclusive favor of the emperor, causing a rift that deepens with each passing day. As the selection process begins for a guardian to look after the newborn child of the emperor’s wife, Empress Yukiko, an unexpected crisis suddenly turns Fuki’s situation upside down. Councilor Otomo views her delivery of an "unwanted child" as a threat, and Fuki becomes the target of a web of schemes spun by the men in power.

Conflicting motives and desperate attempts to “put out the fire” quickly spiral out of control. Meanwhile, a series of inexplicable events occurs, with people spontaneously combusting and being reduced to ashes. The Medicine Seller suspects the work of a Mononoke and sets out to contain it, but he is obstruced by elusive apparitions that seems to act as a group. In reality, this mysterious phenomenon is the children of the Hinezumi, the fire mouse. They seem to be searching for their mother, but she does not reveal herself easily. Why does Hinezumi target those who would harm newborns? What tragedy drives her relentless sorrow as she sets herself ablaze? The Medicine Seller delves into the darkness lurking within the Ōoku to solve the mystery and uncover the mononoke's Form, Truth and Reason: the three elements required to cut it down for good.

[Source: Netflix]

After the fierce battle between the Medicine Seller, wielder of the Sacred Sword, and the Karakasa, followed by the conflict with the Hinezumi — two major incidents born of Mononoke — peace appears, at last, to have returned to the Inner Chambers. Yet the Medicine Seller senses that something has not been laid to rest… and remains ever watchful.

Amidst this uneasy calm, Yukiko, the lawful wife of the Emperor, is blessed with a long-awaited male heir. But the joy is fleeting — the child is lost, despite all prayers offered.
Having wished to change her hollow marriage through the birth of an heir, Yukiko falls into despair… and is drawn into a conspiracy that threatens the very foundation of the Inner Chambers.
Grief without salvation. Rage without refuge. Such emotions begin to take shape. Hokuto Mizorogi, priest of the Inner Chambers’ faith known as “Omizusama,” watches in silence. At the same time, unnatural tremors begin to shake the Inner Chambers. As though something vast crawls beneath the earth, triangular scales drift down from nowhere… and soon, a series of grotesque deaths follows, bodies twisted, crushed, and strangled.

Before the Medicine Seller appears a Mononoke in the form of a great serpent, the snake god. Though it is temporarily driven back with talismans, the Medicine Seller cannot draw the Sacred Sword. To do so, he must uncover its “Shape”, “Truth”, and “Reason”. Only then can the sword be unsheathed, and the Mononoke cut down.

Where was the snake god born? Why does it harbor such overwhelming rage? And why has it risen now?

The answers lie 150 years in the past, in the hidden truth behind the creation of the Ōoku. Long ago, the Inner Chambers were established by Ama-no-Tsubone, wet nurse to the Third Emperor.
Its system sustained an era of peace, and in time came to be revered as “Omizusama”. Sensing a growing disturbance, the Medicine Seller makes his way to the shrine at the heart of the altar, and there, uncovers a truth that was never meant to be spoken.

The tangled fate between the third lawful wife and Ama-no-Tsubone, the secrets of the Mizorogi family, and the true reason behind the successive appearances of Mononoke in the Ōoku all come to light, connecting every thread into one.
Facing what can only be described as the embodiment of the Ōoku’s dark history, the Medicine Seller prepares to stake everything in battle. But the snake god, empowered by centuries of accumulated hatred, possesses unimaginable strength, pushing him into an unprecedented crisis. As death closes in, even more unpredictable horrors unfold.

What fate awaits the Medicine Seller as he faces his greatest trial yet?

[Source: Netflix]