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]