Hisako is Erina's aide. She is a loyal friend to Erina and is seldom 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". 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 Shojo 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.