Sachi Takamiya is a high school student and supporting character with bright orange hair, typically styled in a ponytail featuring strands hanging on either side, and purple eyes.

As one of Akari Watanabe's close friends, she frequently joins Natsumi Ōhashi to form part of Akari's social circle, offering her life advice. Sachi displays an outgoing and assertive personality, often engaging in teasing behavior. She regularly mocks Jirō Yakuin alongside Natsumi, calling him "Virgin kun" to reflect her low opinion. She also enjoys teasing Akari about her romantic interest in both Jirō and Minami Tenjin.

Sachi and her friends hold Minami Tenjin in high regard, striving to gain his favor and frequently complimenting his appearance. She shows concern and slight respect for Shiori Sakurazaka, particularly regarding Shiori's association with Jirō, unaware they were childhood friends.

Her role remains consistent as part of Akari's friend group, providing comedic and social dynamics. No concrete information exists regarding her family background, personal history, or significant character development across official media.