Saya Matsukaze is the younger sister of Mayu Matsukaze, an art teacher at Kawanuma West High School, and attends the same school as a student. She possesses dark hair, typically blue or black, blue eyes, stands 1.54 meters tall, and weighs 45 kilograms, with measurements of 72-56-82.

In contrast to her often air-headed and clumsy older sister Mayu, Saya maintains a calm, collected, and mature demeanor. She frequently acts as the responsible sibling, looking out for Mayu and protecting her from perceived threats, especially male advances. This protective instinct leads to initial distrust of Rin Suzuki, Mayu's eventual husband, despite his genuine kindness.

At Kawanuma West High School, Saya initially serves as student council treasurer before advancing to student council president, reflecting her leadership and responsibility. She assists with school activities like the Kawanuma Festival alongside Mayu and Rin.

Progressing in the manga, specifically in Volume 5 set two years after the anime's events, Saya takes a more prominent role as a senpai to first-year students Yorito Ito and Francesca Homura. Her interactions with them result in various comedic and awkward situations. During this period, she also navigates her own romantic misunderstandings and compromising scenarios.

Saya evolves from a cautious protector of her sister to an individual confronting her own romantic and social challenges. She experiences jealousy and concern over potentially losing her close relationship with Mayu after Mayu's marriage to Rin Suzuki. Her journey illustrates a blend of maturity and typical adolescent vulnerabilities.