Eiko Hozuki is one of the central characters in Dark Gathering, serving as the childhood friend and eventual girlfriend of Keitaro Gentoga, as well as the older cousin of Yayoi Hozuki. She is a university student with a striking appearance, characterized by long light brown hair and dark pink eyes, and she is almost always seen wearing a pair of pink gloves. Her choice of academic major is telling of her interests; despite possessing considerable skill in computer science and programming that could make her a celebrity in the technology department, she chooses to study folklore to better understand the occult world that surrounds her.

Eiko's personality is a complex and contradictory blend of genuine kindness and a deeply disturbed psyche. On the surface, she presents herself as a warm and supportive young woman who deeply cares for Keitaro and her young cousin Yayoi. She is the one who encourages the reclusive Keitaro to re-enter society by finding a job as a tutor, demonstrating her desire to help those she loves. However, this benevolent exterior hides a much darker truth. Eiko possesses a condition known as phobiaphilia, which is a love of fear itself. Unlike Keitaro, who is genuinely terrified by supernatural encounters, Eiko finds them intensely thrilling and exciting. When her physical safety is not at immediate risk, her demeanor can shift to become ferocious and sinister as she revels in the fear and danger of a situation. This twisted enjoyment leads her to manipulate circumstances to place Keitaro, and by extension herself, in perilous situations, as she derives pleasure from the intense emotions that follow.

Her motivations are inextricably linked to this addiction to fear and her obsessive love for Keitaro. She is driven to explore psychic spots and confront malevolent spirits not only to find a cure for the curse she and Keitaro share but also to experience the exhilarating rush of terror. She projects her own phobiaphilia onto Keitaro, believing that he too secretly loves the fear he claims to despise, a belief she uses to justify dragging him further into danger. This warped perspective is part of a larger pattern of extreme behavior, as her affection for Keitaro has manifested as a serious stalking obsession. Her room is famously plastered with photos of him, and she has used her hacking skills to create a pair of glasses for him that are equipped with a hidden camera, allowing her to monitor his conversations, track his location via GPS, and even check his heart rate and body temperature in real time.

Within the story's main trio, Eiko fulfills the vital logistical role that neither Keitaro nor Yayoi can. She is the only one of the three who can drive, serving as the group's mobile shuttle to and from the remote haunted locations they investigate. Her profound expertise with computers and machinery is essential for their ghost-hunting operations. She is capable of hacking into police databases to retrieve confidential case files and provides all the necessary technical equipment to aid in their supernatural investigations. A defining trait that separates her from Keitaro and Yayoi is that she lacks any special spiritual senses; she cannot see ghosts the way they can, although she can perceive powerful or exceptionally resentful spirits. This lack of ability makes her more vulnerable, and she is frequently possessed or cursed simply by being in close proximity to the two spiritual mediums, suffering nearly as much as Keitaro does.

Her central relationship is, of course, with Keitaro. The two have been cursed together since an incident in their past, resulting in a strange, white hair-like nerve growing from each of their hands. While Keitaro hides his curse on his right hand with one glove, Eiko wears gloves on both hands to conceal hers. Her feelings for Keitaro evolve from childhood friendship into a declared romantic relationship, but it is a partnership founded on codependency and a shared, albeit distorted, connection to fear. As the story progresses, Keitaro begins to fully realize the extent of Eiko's true nature. He becomes terrified when she whispers her twisted philosophy into his ear, suggesting that the intense fear and relief he feels during their ordeals is a pleasure he cannot control. This realization creates a new dynamic in their relationship, where her support is both his greatest asset and a source of deep personal dread. She is also a caring, if unconventional, family member to her younger cousin Yayoi, whom she lives with and supports in her quest to find her mother's spirit.

While Eiko does not start with spiritual abilities, she later gains a form of spiritual sight, enhancing her contribution to the group's battles. She also owns a graduate house, a haunted property she acquired for a nominal fee after helping to resolve a case, further demonstrating her deep and practical entanglement with the supernatural world. Her character development across the series reveals her not as a simple hero or villain but as a deeply layered individual whose sunny and helpful disposition is a mask for a fundamentally broken personality that is addicted to fear and obsession.