Sayaka takes a part-time job at the Twin Wings Family Restaurant, only to discover that the establishment specializes in "training" its waitresses to provide provocative services to customers. Coerced by the restaurant's manager—who is also her boyfriend's brother—Sayaka is forced into a series of intimate and degrading acts. Despite her initial resistance and the guilt of betraying her partner, she gradually succumbs to the manager's relentless training and the forbidden pleasure it brings.
While Sayaka deepens her submissive bond with Masashi, her sister Moemi visits the family restaurant and is tempted by its revealing uniforms. Moemi is quickly targeted by Matsura, a disgraced former teacher who uses blackmail to force her into sexual servitude. As Moemi is broken down, it is revealed that Sayaka was once Matsura's victim as well and has now become an accomplice in her sister's corruption.