Ojun is a supporting character in the anime Onihei. She is the young adopted daughter of Heizō Hasegawa, the chief officer who heads the unit responsible for policing arson and theft in Edo. Ojun's background is tied to the criminal world. Her biological father was a thief who had been arrested by Heizō, and her mother, a woman named Ofuji, was connected to the same underworld circle. After her mother died, Ojun was cared for by Ono Jūzō, a doshin who had shown compassion to Ofuji and her child. When Ono Jūzō died in 1787, the girl was looked after by others for a time, but because she was known to be a thief's child, her situation became difficult. Learning of this, Heizō proposed to his wife Hisae that they take her in, and Ojun was brought up in the Hasegawa household as their adopted daughter. Heizō, who was himself born to a concubine and had grown up without knowing his mother, felt a personal sympathy for her circumstances.

Ojun is depicted as a young girl with black hair cut to neck length. In the story she holds a minor role. She is too young to take part in the investigative work that forms the main plot of the series, and she is not shown to have any special abilities or skills. Her significance lies in her place within the Hasegawa family and in what her adoption says about Heizō's character. Taking her in reflects his willingness to show mercy to people whose lives had been touched by crime, especially those who became involved with the underworld through no choice of their own. Her presence in the household also gives a glimpse of the more private side of Heizō's life, apart from his reputation as a feared officer.

Ojun's key relationships are within the Hasegawa household. Heizō is her adoptive father and treats her as his own child, while Hisae accepts her warmly and raises her alongside the couple's biological children, including their eldest son Tatsuzō. The memory of Ono Jūzō, the officer who sheltered her and her mother in her earliest years, is part of the personal history that connects her to the family, as it was through him that she came to Heizō's attention. Her biological parents remain part of her background, but their influence is indirect. Over the course of the series she appears only occasionally, always as a quiet young figure within the family setting, and her story is essentially one of finding a stable home after a difficult beginning.