Himeko Sasaki is a student at Oosugi High School and a recurring character in the series. Her first name, Himeko, carries the meaning of princess or young lady of noble birth.

In terms of personality, Himeko is portrayed as a supportive and comedic figure whose role is unobtrusive within the larger narrative. Her primary motivation is her romantic interest in the protagonist, Eiichiro Maruo, as she harbors a notable crush on him from early in the story. This personal affection drives much of her involvement.

Himeko's main function in the story is that of a spectator and a source of support. She is known for attending most of Eiichiro Maruo's tennis matches, often in the company of her friend and classmate, Kojirou Kageyama. This consistent presence establishes her as part of the group of peers who follow and encourage the main character's athletic journey. Her key relationship is with Kojirou Kageyama, as the two are frequently seen together as part of the supporting audience at tennis tournaments.

Regarding her development, Himeko does not undergo significant growth or change throughout the series, remaining largely a static supporter whose character is defined by her cheerful attendance at matches and her ongoing crush on Eiichiro. In terms of notable abilities, she does not possess any athletic or tennis-related skills that impact the plot, as her role is not that of a competitor but rather that of a schoolmate and spectator.