Saku Tōyama serves as a member of Genius 4 (G4), the police investigation unit within the franchise. She consistently presents a soft-spoken and reserved demeanor. Visually, she is defined by prominent headphones constantly framing her appearance and is frequently seen with a lollipop as a signature accessory. She holds a particular interest in retro technology. Within G4, she operates under the leadership of Kokoro Akechi. Her surname, Tōyama, deliberately references the historical Edo-period samurai official Tōyama Kagemoto, aligning with the franchise's naming conventions, while her given name Saku (咲) carries the meaning "blossom".