For decades, an aging slave has been passed from one mistress to another, used and discarded as nothing more than a tool. Always prioritizing his mistress's pleasure, he endured endless servitude even as his body broke down. But as he grew older, finding new mistresses became impossible, and unable to work, he fell into days of despair and tears. Enter Rei, the dominatrix instructor at the "Slave Rehabilitation Training Center"—a facility dedicated to retraining elderly and discarded slaves, restoring them into functional servants fit for society once more. Today, another aged slave arrives at the facility. Under Rei's merciless retraining, he will be pushed through trials so severe that, even as he weeps, he must endure and overcome.