Miyashita is a classmate of the Marui sisters and can often be seen hanging around with her friends Yuki Yoshioka, Miku Sugisaki, and Mitsuba Marui (when she isn't being a jerk).
The anime describes her as the only well adjusted person in her class, however she has an odd obsession with understanding and becoming friends with Hitoha Marui. This has led to many misunderstandings between the two of them and others, resulting in many thinking that she has a yuri crush on Hitoha.
Miyashita is a character in both Mitsudomoe anime series, Mitsudomoe and Mitsudomoe Zoryochu!, published by Aniplex with animation production by Bridge and the manga series Mitsudomoe, published by Akita Shoten and serialized in Weekly Shonen Champion. Miyashita's original design is credited to manga writer and illustrator Norio Sakurai while her anime version is credited to Takaharu Okuma. Miyashita makes her first voiced anime appearance in Mitsudome episode 5, "Bra! Bra! Pig!".