Fūko Andō is a twenty-four-year-old graduate student of clinical psychology who becomes the primary guardian of her four-year-old niece, Nagisa. The child is the daughter of Fūko's older brother, Takanori, and his partner, Akane, the latter of whom died after giving birth. Takanori is largely absent from the child's life, living in a state of retirement, which leaves Fūko responsible for raising Nagisa.

As a student of psychology, Fūko possesses an academic and analytical mind, though her most defining role is that of a caregiver. Her personality is defined by her protective instincts toward her young niece. Despite the challenges of raising a child while completing her own education, she demonstrates a deep sense of familial duty and resilience. As the story progresses, Fūko becomes aware that Nagisa is not an ordinary orphan. She discovers that the child is mysteriously connected to a cursed video clip incident that occurred five years prior, forcing her to confront terrifying supernatural forces. Her motivation shifts from simply providing a stable home for Nagisa to investigating the dark, mystical circumstances surrounding the girl's birth and her link to the malevolent spirit Sadako.

Fūko's key relationship is with her niece, Nagisa. The child exhibits two distinct behavioral states, ranging from a quiet, almost detached demeanor to a menacing and unsettling presence, which complicates Fūko's efforts to understand and protect her. Her brother Takanori remains a peripheral figure in the narrative, having distanced himself from both his daughter and the mysterious events of the past, leaving Fūko to face the escalating horrors alone. Regarding her character development, no reliable direct information exists. Regarding notable abilities, no reliable direct information exists.