Hisako is Mizuho's homeroom teacher to his class of 3-A and is the one of the only people in the entire school who knows that Mizuho is in fact a boy, other than Mariya, the headmistress and later Shion and Ichiko. She has a helping personality and even told Mizuho to come to her if anything was bothering him. She often gives out candy to her students. Hisako makes an appearance again for the sequel Otome wa Boku ni Koishiteru 2: Futari no Elder, this time as Chihaya's homeroom teacher and the school's acting principal. She also knows his secret like Mizuho before him. Her appearance has changed since Mizuho's time at the academy, she has longer hair in particular.