She, along with Alice Nakiri and Ryō Kurokiba helped Erina to escape from her estranged father, Azami Nakamura and taking refuge in Polar Star Dormitory to protecting Erina away from Azami. She and Erina insisted to join Sōma and the Rebels to put an end to Azami's insolence. However, She and most of the Rebels (except Sōma, Erina, Megumi and Takumi) were expelled by Azami's rigged promotion exams after defeated by the Elite Ten under Azami. After the Elite Ten defeated, her expulsion has been revoked.
4 months after Central's defeat, Hisako resumed her position as Erina's secretary.
Hisako has short pink hair with bangs that reach to the length of her chin. In the early parts of the series, she has a normal fringe reaching the length of the eyebrows. Later on, her fringe parts to the left.
She normally wears the standard Tōtsuki seasonal uniforms, even when not in school. She wears a plain white chef's uniform when she cooks. Hisako has been shown wearing glasses when working behind a computer.
Her measurements are: bust 80 cm, waist 56 cm and hip 79 cm (31-22-31).
Hisako is a loyal friend to Erina and is almost never seen away from her. As her secretary, she helps organize Erina's tasks and assignments to allow her to focus on her work, showing an impressive amount of time management and secretarial skills, even more so considering that she is only a high school student. Much of Hisako's ambitions are to help out Erina and make sure that she stays at the top of the class, with Erina standing above her as her "Empress". This means that she tends to care more for Erina than she does herself, which has been the case since they were kids. Hisako is always fine following behind Erina and was fine being that way since childhood. She also helps introduce some modern things to Erina such as Shōjo manga, which she buys for her upon request. Much like Erina, Hisako is generally stubborn and prideful, often belittling others, usually in Erina's stead.
However, her pride as Erina's closest ally was severely damaged when she lost her Quarterfinal match in the 43rd Annual Tōtsuki Autumn Election main tournament against Akira Hayama. Since then, she sulked much more, believing that she was no longer worthy to be Erina's secretary, let alone her friend, despite Erina's personal protests. However, thanks to Sōma's advice, her resolve has changed. Now she wants to stand beside Erina rather than following behind. She has become much more friendly and even befriended Sōma during their week together, despite previous feelings towards him.