Hajime Shibata is introduced in the first season of the anime as a major character whose actions create a central point of opposition to the series' supernatural premise. He is a freelance journalist and a single father, profoundly marked by a tragic past that shapes his worldview and drives his actions throughout the story.

Before becoming a freelancer, Hajime was a top reporter for a political and economic magazine, known for his skill in investigating scandals. However, his career came at a great personal cost. During his college years, he met and eventually married Ayumi Ogawa, but his work often left her feeling neglected. The marriage shattered when Hajime, while on a stakeout investigating a politician's affair, discovered that his wife was the politician's secret lover. Blinded by betrayal, he expelled Ayumi from their home and forbade her from seeing their daughter, Tsugumi. Shortly after, Ayumi died in a car accident, an event Hajime witnessed and for which he carried immense guilt, believing his harsh rejection led to her death. This trauma is the foundation of his firm belief that revenge is wrong and only leads to further suffering.

As a freelance journalist, Hajime supports himself and his daughter through morally ambiguous work, including blackmailing celebrities to keep their scandals out of the press. Despite this cynical livelihood, he is portrayed as a caring, if often preoccupied, father. His relationship with his daughter Tsugumi is his most important personal connection. She often calls him by his first name, reflecting their close and informal bond, and he frequently finds himself unable to resist her arguments. Hajime appears as a man with light black hair, dark gray eyes, and an unshaven stubble, typically wearing a brown jacket and jeans, giving him a somewhat worn and serious appearance.

Hajime's role in the story begins when he investigates rumors of the "Hell Correspondence," a website that allows people to send their tormentors to Hell. This investigation becomes personal when his daughter Tsugumi develops a supernatural telepathic link with Ai Enma, the Hell Girl herself. Through this link, Tsugumi experiences visions of Ai and the people who seek her services. Hajime uses this connection to track down potential clients, intervening in an attempt to convince them not to pull the red string on the straw doll and condemn themselves and another to damnation. His efforts are rarely successful, and his persistent meddling makes him a recurring obstacle for Ai and her companions, who see him as a nuisance.

His determination to stop the Hell Correspondence eventually uncovers a deep, ancestral connection to Ai Enma. Hajime discovers he is a descendant of Sentarou Shibata, a villager from 400 years ago who was Ai's close cousin and protector. When Ai was sacrificed to appease the local mountain god, Sentarou secretly kept her alive by bringing her food. However, when the villagers discovered Ai had survived, Sentarou betrayed her by participating in the ritual that buried her and her parents alive, an act that led to Ai's death, resurrection, and vengeful destruction of the village. This lineage explains Tsugumi's psychic connection to Ai and makes Hajime a target for Ai's lingering hatred of Sentarou.

Throughout the first season, Hajime evolves from a man determined to stop the cycle of revenge into someone worn down by his repeated failures. His resolve is severely tested when Ai uses her powers to force both him and Tsugumi to relive the night of his wife Ayumi's death, exposing his long-held guilt. In a climactic confrontation, Ai manipulates Tsugumi, attempting to make her pull the string and condemn Hajime to Hell for his role in her mother's death. However, Tsugumi refuses, professing her love and forgiveness for her father, an act of compassion that foils Ai's plan.

After this ordeal, Hajime abandons his mission to stop the Hell Correspondence, emotionally exhausted by his futile struggle. In the second season, it is revealed that he channeled his knowledge into writing a biography about Ai Enma, intended as a guide for others who might become entangled with her. Shortly after completing this book, Hajime mysteriously disappears. His ultimate fate is unknown, as even Ai's companions cannot confirm what happened to him, though he was not sent to Hell.

Hajime possesses no supernatural powers. His notable abilities are his skills as a researcher and investigator. He is persistent, detail-oriented, and capable of connecting disparate clues to uncover hidden truths. His primary strengths lie in his tenacity and his profound, if cynical, understanding of human nature and the motives behind vengeance.