Yayoi Toreishi holds the position of second eldest among the Toreishi siblings. Her documented age is 18 during the main events, turning 19 by the time of '95 Song of the Wind, born on March 7.

Characterized as a tomboy, she initially felt reluctant about participating in idol activities but joined anyway, driven by not wanting to be left out. She possesses a strong athletic streak, throwing herself into various sports competitions with fierce competitiveness, refusing to hold back even against her own sisters.

Her interactions with the youngest sister, Mina, often involve quick, physical reactions to annoyance or teasing, typically resulting in Yayoi slapping Mina's face. Within her squadron, Yayoi operates in a frontline combat role alongside sisters Kanna and Satsuki. Unlike Kanna's preference for tactical reserve, Yayoi shows less hesitation to dive into direct combat and has coordinated tactically with Satsuki during aerial battles.

She pilots the personally assigned HB-02 aircraft, noted for its heavier firepower compared to other squadron aircraft and its reliance on Vertical Take-Off and Landing (VTOL) capability, allowing deployment directly from their base. During idol music performances, she occasionally sings duets with the eldest sister, Kanna.

Her operational record includes taking part in an idol-themed water contest aboard the USS Enterprise. This event was interrupted by an unauthorized aircraft intrusion. Following engagement protocols, Yayoi participated in the defensive interception and simulated elimination of the intruder, openly relishing the successful takedown.