Shibata Tsugumi emerges at age seven, displaying remarkable maturity and independence. She manages household chores, cooking, and grocery shopping alone, compensating for her father Hajime Shibata's frequent absences. Her brown hair and eyes remain constant features. In childhood, she wears braided ponytails secured by black hair bands and pins her bangs with a red clip. She affectionately addresses her father as "Hajime-chan," reflecting their unique bond.

Her mother, Ayumi Shibata, perished in a car accident shortly after divorcing Hajime, leaving Tsugumi as his only family. A pivotal moment occurs when Tsugumi encounters Ai Enma at a train crossing, forging a telepathic link. This connection forces involuntary visions through Ai's eyes, aiding Hajime's journalistic investigation into the Hell Correspondence website by revealing client and target details. Tsugumi later uncovers her lineage: she descends from Sentarou Shibata, Ai's cousin who escaped the village fire Ai ignited centuries prior. Ai extends her ancestral grudge to Tsugumi and Hajime, attempting to coerce Tsugumi into sending Hajime to Hell by falsely blaming him for Ayumi's death. Tsugumi refuses, defiantly returning the cursed doll to Ai out of loyalty to Hajime.

Years later, Hajime publishes a book on Hell Girl before vanishing. Appearing older with hair reaching her mid-back, Tsugumi briefly interacts with a detective researching Hell Girl, implying Hajime left the book for those in need. She confirms Hajime abandoned efforts to stop the Hell Correspondence, with some sources suggesting potential off-screen death.

By *Three Vessels*, Tsugumi is an adult school nurse, retaining her mid-back-length hair and often wearing a lab coat. Her demeanor shifts toward cynicism and resignation regarding the Hell Link's inescapable cycle. She assumes the nursing position at Yuzuki Mikage's school after foreseeing Yuzuki's fate, attempting to steer her away from becoming the next Hell Girl. Tsugumi discerns Yuzuki's fading existence, revealing Yuzuki died years earlier and lives an illusion. When Yuzuki accepts the Hell Girl mantle, Tsugumi departs, uncertain if Yuzuki later finds peace.

Her involuntary ability to see through Ai's eyes persists uncontrollably into adulthood, forcing her to witness Hell Link users and victims. In *The Fourth Twilight*, she works as a caregiver at a nursing home, tending to Sakura Kubota. After Sakura enacts revenge via Hell Correspondence, Tsugumi glimpses Ai outside before her disappearance.