Saku Tooyama serves as a police officer within the Genius Four, an investigation unit operating in the Holmes Detective Academy setting. Her characterization remains consistent across all media, including seasons, specials, the movie *Gekijōban Tantei Opera Milky Holmes: Gyakushū no Milky Holmes*, and spin-offs. She possesses light pink hair styled with spiky bangs and waist-length waves, violet eyes, stands 156 cm tall, and weighs 41 kg. Headphones are a constant part of her appearance, and she is almost always depicted with a lollipop in her mouth, forming signature visual elements.

Her personality is soft-spoken, stoic, and kuudere, exhibiting a reserved demeanor with rare overt emotional displays. A notable affinity for retro technology frequently features in her scenes. Professionally, she operates as part of the Genius Four unit, engaging in group investigations and confrontations against groups like the Thieves' Empire. In the movie *Gyakushū no Milky Holmes*, she appears alongside the Genius Four during a three-way battle involving Milky Holmes and the Thieves' Empire, maintaining a supportive role without unique plot involvement.

No significant character development, backstory revelations, or personal arcs are documented for Saku Tooyama across official media. Her portrayal remains static, emphasizing her established traits—headphones, lollipop, interest in retro technology, and stoic professionalism—without evolution or deeper exploration. Her surname, Tooyama, references the historical figure Tōyama Kagemoto and combines "distant, far" (遠) with "mountain, hill" (山). Her given name "Saku" (咲) translates to "blossom."