Emi Kino is a core member of the Superhuman Bureau and a central figure in the story. Her background is defined by her unique heritage: she is a half-human, half-youkai hybrid, born from a union between a human and a supernatural being often referred to as a yokai or ogre, with specific sources identifying her youkai lineage as that of a kitsune, or fox spirit. This dual nature shapes her entire existence, giving her a foot in both the human world and the world of supernatural creatures. Since childhood, her life has been deeply intertwined with that of Jiro Hitoyoshi, as the two have lived together since they were in elementary school, establishing a profound and lasting bond.

In terms of personality, Emi presents a calm, somber, and often inscrutable exterior. Her moods can be difficult to read, lending her an air of mystery and unpredictability. Despite her often serious demeanor, she is driven by a deeply held personal dream: she wishes for a world where youkai and human beings can coexist in harmony. This motivation is a direct result of her own hybrid identity and the tensions it creates. One of her most defining personality traits is her fierce protectiveness over Jiro. She has harbored romantic feelings for him since their youth, once even claiming to be his fiancée. This leads to a noticeable jealousy towards Kikko Hoshino, whom she views as a rival for Jiro's affections and dislikes seeing getting close to him. Her actions are not solely personal, however; she is a dedicated, if morally complex, agent whose loyalty to the Bureau is sometimes at odds with her own agenda.

Within the Superhuman Bureau, Emi serves as a highly skilled operative, specializing in tracking and possessing a broad range of uncanny knowledge and strange skills. Her role often requires her to act as an intermediary with the supernatural world. Because she is less than fully human, she is a revered figure among some non-human communities, such as the secret subterranean civilization, where she is hailed as their ogress princess. Her role in the story frequently puts her in morally gray situations, as she is not above manipulating events or people, including her colleague Kikko, to steer them toward a particular outcome. She is fundamentally a pragmatist who works within the system while also challenging it, as seen when she opposes government policies that scapegoat superhumans for disasters, choosing instead to protect the innocent and expose corruption.

Her most significant relationship is undoubtedly with Jiro Hitoyoshi. Their bond, forged in childhood, is central to the plot as their fates are closely linked. She is fiercely loyal to him and acts as a guardian of his most dangerous secret. Her connection with Kikko Hoshino is more adversarial, defined by a rivalry for Jiro's heart. She harbors a personal animosity toward Kikko, seeing her as an interloper. Emi also has notable interactions with the supernatural beings of her world; many revere her, calling her their princess, which gives her a unique form of influence and authority that other human characters lack.

Throughout the narrative, Emi experiences significant development as her personal convictions are tested. Her dream of harmonious coexistence is challenged as government authorities increasingly crack down on superhumans and blame them for societal problems. This forces her to navigate a treacherous path between her duty to the Bureau and her desire to protect her own kind. Her relationship with Jiro also evolves, fluctuating between unwavering devotion and moments of ambivalence, complicated by his own unpredictable actions and her own complex schemes. Her past also contains fragmentary, unresolved chapters that hint at deeper secrets yet to be uncovered.

Emi possesses a set of notable abilities rooted in her youkai heritage. She has demonstrated the power of shapeshifting, allowing her to assume human disguises by taking an image from a magazine. Her true form is said to resemble a human with a fox head. She can also control birds by whistling, commanding them to do her bidding; the birds refer to her as their princess. Additionally, she can summon and control spirit-like foxes, which she uses for tracking and surveillance purposes. Perhaps her most critical and unique ability is her power over Jiro. She is the only person who can safely restore the magical locks that bind and suppress Jiro's immense, uncontrollable flames, preventing him from going on a catastrophic rampage. She wears a distinctive outfit that includes a white and blue outlined coat over a dark gray long-sleeved shirt, a cranberry pencil skirt, and high dark gray boots with heels and golden buttons.