Tōtsuki Culinary AcademyEdit
Erina has been Hisako's best friend since they were young children. Amazed by her prestige and abilities, Hisako devoted her all into learning the Arato family's legendary medicinal cooking techniques so she could serve Erina. Since then, Hisako has served as Erina's secretary, choosing jobs for her and is generally wherever Erina is.
Erina deeply cherishes Hisako as she is the only friend she has had and was visibly upset by Hisako's sudden leave of absence after her defeat in the Autumn Elections. Though their bond of friendship is tight, she was unable to oppose Azami's decision to relieve her of her duties as Erina's secretary. Erina's inability to object to her father also made this impossible to do.
Erina's former arch rival who hails from the humble Restaurant Yukihira. Upon her encounter with Sōma, Hisako deemed the boy was "disrespectful" to Erina when he nonchalantly chatted with Erina despite their different position. Because Erina deemed Sōma as a "threat" in her life, Hisako made an effort into trying to send Sōma packing away from the Tōtsuki for Erina's sake.
Like her fellow students, Hisako belittled Sōma despite his ongoing success until the Autumn Election Quarterfinals where she was defeated by Akira in a hamburger battle. Unbeknownst to Hisako however, Sōma was among the Autumn Election Finalist and ranked in Second Place (tied with Ryō). Even when she became Sōma's unexpected partner during the Stagiaire event for the Restaurant Mitamura, Hisako remained skeptical upon Sōma until she witnessed his uncanny performance by handling even the overcrowding customers in the restaurant. Despite Hisako's initial hostile behavior to him, Sōma himself showed no hostility to her and even has a one-sided friendly attitude towards her. During their partnership in the Stagiaire event, Sōma helped her regain her confidence.
Because of Sōma's assistance in getting her to try and stand beside Erina as an equal rather than in her shadow, Hisako now displays a much friendlier attitude towards Sōma and enjoys his company, something that even Erina finds hard to believe as she was surprised the two had become good friends.
In their middle school years, Hisako was challenged to a Shokugeki by Nao for the position of Erina's secretary. Hisako won the duel and Nao was forced to say a minimum of 50 feet away from Erina at all times. Since then, Nao sent 30 letters daily to Erina, though Hisako intercepted them and disposed of them immediately. The two finally had an opportunity to face each other during the 43rd Annual Tōtsuki Autumn Election during the preliminary round. In the end, Hisako's dish was superior and even Nao was temporarily "exorcised" as a result. Unfortunately for Hisako, Nao developed a similar stalker crush on her as she did for Erina even calling her "Hisako Onee-sama".
This new attention and change in demeanor causes both confusion and uneasiness for Hisako.
Hisako's first opponent for the Autumn Election Main Tournament was Akira. Both he and Hisako shared their professionalism in food forte, especially in spices and herbs. Because Akira was planning to replace Erina as the Elite Ten Council member, Hisako took a dislike to him and belittled Akira for thinking he could defeat Erina. Unfortunately, not only did she lose to Akira in a hamburger match but also was criticized by Akira for her lack of ambition and limited vision of the culinary world, as well for her loyalty towards Erina which he deemed her as Erina's "No.2".
Her defeat at his hands caused Hisako to feel extremely upset and ashamed of herself and she was unable to face Erina afterwards.
The owner of the Western Cuisine Mitamura and also Hisako's supervisor during the Stagiaire event.