Shien is a ninja descendant collaborating with police to infiltrate an organization running underground fighting tournaments. Her primary mission is rescuing her kidnapped younger sister, Kuureha. The organization sets Shien's tournament victory as the condition for Kuureha's release. Despite Shien's participation, Kuureha had already been brainwashed, rendering Shien's objective unattainable regardless of the tournament's outcome.

Driven by a strong protective instinct toward her sister, Shien agrees to the dangerous tournament under the organization's terms. She wears predominantly dark clothing reflecting her ninja heritage, including fingerless gloves. Her physical portrayal emphasizes traits associated with the "Buxom Is Better" trope. In combat, she operates as a "Fragile Speedster," relying on agility and speed over physical strength.

Before her critical fight, the organization sabotaged Shien by forcing her to consume an aphrodisiac, severely impairing her combat effectiveness. During the tournament, she was subjected to witnessing the sexual assault of Kuureha by two androids, categorized under the "Forced to Watch" trope. Her narrative concludes with Kuureha undergoing a "Face Heel Turn," ultimately serving the organization after being subjugated.