As a young teen, Hinami was shy with a very gentle heart. She was also eager for knowledge and fond of reading in order to learn. She cared deeply for Touka and Kaneki, whom she dubbed 'big sister' and 'big brother', respectively, constantly expressing sadness and worry for the two's unhappiness. She also had a very pacifistic nature, having no intention to avenge her mother and father despite loving them so much. Hinami gradually coped with the deaths of her parents better, and obtained a very cheerful attitude.

After she had matured, Hinami's demeanor has become much more calm, collected, and somewhat distant. Her experiences since Kaneki's disappearance and the CCG's new agenda has caused her to lose much of her previous cheerful stance and instead take on a jaded, realistic outlook on life. Since joining Aogiri Tree, Hinami is no longer terrified of smelling or seeing death. However, she is still reluctant to kill. She believes this to be her weakness and the reason people she loved left her.

Hinami and her mother, Ryouko Fueguchi, were the frequent visitors of Anteiku, an establishment dedicated to helping those like them, and they were provided with food there. It was her first meeting with Ken Kaneki, her 'big brother'. Upon discovering that they liked the same author, he taught her some words from the book, and she asked him to continue teaching her.

Later, while Hinami and her mother were walking back from the bookstore, four ghoul investigators, including Koutarou Amon, Kureo Mado, Yasutomo Nakajima and Ippei Kusaba, lured the two into an alley to annihilate them. Ryouko told her daughter to run while she held the attackers back. During her frantic escape, Hinami ran into Kaneki and begged for his help, but only returned in time to witness her mother being killed by Mado. When reading a newspaper detailing Kusaba's death, Hinami realized Touka had killed the investigator as revenge and decided to run away. Touka found her in a distraught state and comforted her, only to be interrupted by the appearance of Mado. Hinami helplessly watched her sister figure battle and slowly lose against the investigator, eventually releasing her own kagune and rendering Mado helpless. As Hinami cried over the loss of her parents, a weak and injured Touka finished off Mado. Renji Yomo and Kaneki rushed to Hinami's and Touka's whereabouts and accompanied them back to Anteiku. During their walk back, Hinami asked if it was right for her to live and Kaneki answered that he believed it to be Ryouko's will.

When he was kidnapped later, she decided she wants to repay him and joined the group in order to rescue him. She was the one who ultimately managed to figure out where he was held.