Yōki is a fair-skinned oni with short red hair, crimson eyes, and elf-like ears, featuring two horns tipped in purple and a devil-like tail. She typically wears a sleeveless black hooded tube top with a zipper, shorts, gloves, and ankle boots. As an intermediate-level torturer (lieutorment) in the Hell-Horde, Yōki specializes in friendship-based interrogation techniques alongside her cousin Inki. Their methods center on rapport-building group activities such as video games, beach outings, and theme park visits. Yōki later earns a promotion to harm-marshal, a higher-ranking torturer position, after incorporating the Hell-Lord's daughter Mao-Mao into their tactics for increased effectiveness. Yōki exhibits a cheerful, energetic personality, often acting as a supportive figure to both Inki and their imprisoned Princess. She deeply values friendships, quickly initiating bonding activities like exchanging phone numbers and inviting the Princess to an amusement park. Competitiveness defines her, especially during video game sessions and physical challenges like balloon-popping sword fights at the beach, where she employs a water-based gatling gun. However, she consistently loses video games to both Inki and the Princess. Her interests include horror-themed activities, firearms, and recreational outings. She once proposed hide-and-seek in a "haunted" building filled with costumed monsters and used a concealed water gatling gun during a beach competition. Yōki also demonstrates courage in physically demanding "tortures," such as a large-scale eating contest where she consumed 57 bowls of wanko soba. Yōki initially had no ambition to become a torturer but chose the career to stay close to Inki. During high school, they deliberated their future together and ultimately joined the Hell-Horde's interrogation division simultaneously, highlighting her prioritization of personal bonds over professional goals. Her interactions with the Princess evolve from tactical interrogation to genuine camaraderie. When Yōki fell ill and missed a planned ghost-house session, the Princess voluntarily revealed a secret while visiting to check on her. Similarly, Yōki's invitation to the theme park stemmed from authentic enthusiasm rather than purely strategic motives.