Gyokumen Koushou is a central antagonist in the anime Saiyuki Reload, identified as a youkai, or demon, who serves as the mistress to the powerful demon king Gyumaoh. Proclaiming herself as Lady Koushou and also known as Princess Jade, her primary driving motivation is the resurrection of her lover, Gyumaoh, with the ultimate goal of reviving him and finally marrying him. Her entire scheme revolves around obtaining the Heaven and Earth Scripture, a sacred text also known as the Five Sacred Sutras, which is necessary to complete the revival process.

Personality-wise, Gyokumen Koushou is portrayed as extremely cruel, selfish, and manipulative. She demonstrates a willingness to sacrifice anything and anyone to achieve her goals, often appearing to take a certain degree of enjoyment in her malicious acts. This lack of empathy extends to her own family. She is the biological mother of Lirin, a daughter she had with Gyumaoh, yet she shows no maternal care or affection towards her. Instead, she views her own daughter as nothing more than a tool to be used when it serves her purposes. Her relationship with Kougaiji, Gyumaoh's son from his wife Rasetsunyo, is similarly transactional. She manipulates Kougaiji by promising to revive his mother from a stone curse, using this pledge as leverage to force him to retrieve the sutras from Genjyo Sanzo and his party.

Within the story of Saiyuki Reload, Gyokumen Koushou functions as a primary antagonist and the mastermind behind the chaos engulfing the land of Shangri-La. She is held responsible for breaking the five-hundred-year-old seal of Houtou Castle, an act that freed most of its demonic occupants and set the stage for her plans. To achieve the resurrection of Gyumaoh, she forms a critical alliance with the twisted bioengineer Dr. Ni Jianyi. Together, they employ a forbidden mixture of youkai magic and human science. Gyumaoh's body is stored in a special incubation chamber, requiring the sutras for the revival to be complete.

A key part of her strategy involves the use of the Minus Wave. Gyokumen Koushou and Dr. Ni Jianyi release this wave across all of Shangri-La, a phenomenon that brainwashes youkai, driving them to madness and causing them to turn violently against humans. This wave also compels the affected youkai to do her bidding, specifically to assist in obtaining the sutras in the name of Gyumaoh's revival. She further invests her resources in Dr. Ni's many inventions, which combine magic and science into deadly weapons used to track down the sutras and eliminate the Sanzo party, though these attempts are consistently evaded by the group.

In terms of notable abilities, Gyokumen Koushou is not primarily a frontline fighter. Her power lies in her strategic cunning, her capacity for manipulation, and her control over vast resources. Her most significant ability is her authority to command other youkai, directing them to carry out her will on a massive scale. Her influence is directly tied to the Minus Wave, which acts as a tool for mass control and chaos. While she is not personally seen engaging in combat, her effective leadership of the revival project and her ruthless management of characters like Kougaiji and Dr. Ni makes her a formidable and persistent threat throughout the series. As the series progresses into Saiyuki Reload Blast, it is revealed that she has come into possession of at least two of the sacred sutras, bringing her closer to her ultimate goal of reviving the demon king.