Saku Tooyama is a key member of the elite Genius Four police investigation unit, known for her consistently stoic demeanor and soft-spoken nature. Her striking visual design features long, light pink wavy hair cascading past her hips and distinctive violet eyes. She stands 156 centimeters tall and weighs 41 kilograms.

She is almost never seen without her signature headphones and typically has a lollipop in her mouth. This investigator also demonstrates a particular interest in retro technology. Her standard outfit is a uniform incorporating elements such as a miniskirt, coat, boots, belt, ribbons, and a pendant necklace.

Within the Genius Four, she operates alongside colleagues Kokoro Akechi, Tsugiko Zenigata, and Hirano Hasegawa. Saku appears throughout the franchise, including the original anime series, Act 2, Futari wa Milky Holmes, Tantei Kageki Milky Holmes TD, the Milky Holmes' Counterattack film, and various OVAs like Fun Fun Party Night and the Alternative specials. Her core personality traits and visual design remain steadfastly consistent across all these appearances.