Yuuki Miyagawa operates as a covert agent for a government agency, specializing in intelligence gathering. Her assignments involve infiltrating organizations like a pharmaceutical company suspected of illegal drug production. During one operation, her identity was exposed alongside fellow operatives Reiko Carrere Yukiko and Kana Morishita, resulting in their capture. Company researchers detained them, conducting experimental procedures under the pretense of scientific study while subjecting them to molestation.

She possesses brown hair, yellow eyes, and stands 1.65 meters tall. Her recorded physical measurements are 115-59-98. She holds Japanese nationality and is occupationally designated as "chouhouin" (spy).

In the original source material, her specific task was an internal investigation within the pharmaceutical company. The exposure of her undercover identity led to extended captivity and systematic mistreatment.