Kazuo Saiga, operating under the alias "Siberia Tiger," is an adult male antagonist with black hair, brown eyes, and facial hair, consistently depicted wearing gloves and identified as a smoker. He serves as the primary antagonist during a train sequence set in the Russo-Japanese war era, orchestrating threats against passengers and masterminding the onboard conflicts. Saiga engages in a physical confrontation with Youko Sumeragi, an undercover agent disguised as a male diplomat. In this fight, he leverages superior combat experience to overpower her, landing strikes to her stomach and mocking her perceived inexperience. He pins her against a wall and delivers another blow using his thighs, resulting in her being thrown from the train window.