Miyo Takano, born Miyoko Tanashi, is a central figure in the story who initially appears as a friendly and enigmatic nurse at the Irie Clinic in the village of Hinamizawa. She has long blonde hair and often wears a nurse uniform or, when conducting official business, a military-style outfit. She presents herself as an upbeat and approachable person who enjoys sharing occult stories about the village's past, often giving different versions of the local curse to different listeners. This cheerful exterior, however, masks a far more calculating and ruthless interior.

Her background is marked by deep trauma. After her parents died in a car accident when she was young, she was sent to a harsh orphanage where she suffered abuse. She attempted to escape with a group of friends but was caught after calling for help from the only number she knew, that of Hifumi Takano, a researcher. He adopted her, and she changed her name from Miyoko Tanashi to Miyo Takano. Witnessing her adoptive grandfather's research on Hinamizawa Syndrome being dismissed and disrespected by government officials left a lasting scar on her. After his death, she dedicated her life to validating and completing his work. She rose through government ranks, secured funding for a research project in Hinamizawa, and, alongside Kyousuke Irie, discovered the pathogen behind the syndrome. She also developed both a cure and a drug that could trigger its fatal symptoms.

Miyo's motivation is rooted in a desperate need to give meaning to her and her grandfather's life work. She sees the completion of the research as a path to leaving a lasting mark on the world, which she equates with achieving godhood. When government support for her project was withdrawn and she was ordered to conclude research quietly, she saw this as a complete negation of everything she had fought for. This drove her to orchestrate the Great Hinamizawa Disaster, a plan to release a deadly gas to wipe out the village and cover up the syndrome, in order to force the government to acknowledge the research out of fear.

In the story, she is the primary antagonist and the true mastermind behind the series of mysterious deaths known as the curse of Oyashiro. She operates from the shadows, using an organization known as the Mountain Hounds to carry out her plans. A key part of her scheme is her Queen Carrier theory, which posits that the death of the queen carrier, Rika Furude, would cause the entire village to suffer a fatal outbreak of Hinamizawa Syndrome. She repeatedly fakes her own death and manipulates events to murder Rika, hoping to trigger this mass disaster. Her role is that of a brilliant but deeply obsessive schemer whose actions create the cyclical tragedies that define the narrative.

Her key relationships are largely defined by manipulation and shared goals. She has a close bond with Jirou Tomitake, a photographer who is both a friend and lover, though she ultimately sacrifices him when it suits her plan. She works with Kyousuke Irie, who assists her research, though he is not fully aware of her ultimate intentions. Her most significant relationship is with Rika Furude, whom she targets as the linchpin of her plan. She also has a complex connection with Satoko Hojo, as both share ties to the village's painful history. With the Mountain Hounds, she gives orders as their commander, treating them as tools.

Miyo undergoes little traditional character growth, as her core obsession remains fixed throughout most of the story. However, her background is gradually revealed, shifting her from a mysterious supporting character into a fully realized antagonist whose cruelty is explained by her past suffering and desperate need for validation. In the final arcs, she is confronted by the main characters, and her plans are ultimately thwarted. Some interpretations of her later actions suggest a faint possibility of redemption, but her defining trait remains her unyielding dedication to her goal.

Her notable abilities lie in her intellect and strategic planning. She is a master of manipulation and deceit, capable of faking her own death, framing others, and pulling the strings of a large organization from behind the scenes. She is highly skilled in psychological manipulation, using fear and superstition to control the villagers. While she has no supernatural powers, her sharp analytical mind and willingness to go to any lengths make her a formidable opponent. She also has practical skills from her roles as a nurse and a government operative.