Katsuie Shiraishi serves as bodyguard to Oichi Tenma within the International Battle Spirits Association (IBSA). He possesses a large frame, black hair spiked upward at the back, and grey eyes, typically dressed in a purple suit over a pink shirt with a white tie. His personality is defined by unwavering loyalty to Oichi and the IBSA, reacting explosively to any perceived disrespect toward her.

Accompanying Oichi on an observation mission for her safety, Katsuie battles Yukimura on her orders, wagering a Soul Burst card, but suffers defeat. He later joins a special IBSA representatives team alongside Hanzou Hyakki and Okuni Midoriyama. Despite initial doubts about their abilities, he eventually accepts them as teammates. During championship events, he faces Dairokuten Maou in battle, only to suffer another decisive loss. Shifting to a supportive role, he notably encourages Yukimura during Yukimura's confrontation with Nobunaga to stop Nobunaga's plans. The series concludes with him participating in Nobunaga's farewell as Nobunaga departs Japan with Toukichirou Mashira and Ranmaru Shikigami.

In card battles, Katsuie employs a dual-colored purple and white attribute deck. This deck utilizes spirits, braves, and bursts, featuring key cards like The WhiteSnakeEmperor Aldius-Viper (purple spirit), The FlashSoulBlade Lightning-Shion (purple brave), and The IceHero Mibrock-Baragan (white spirit). His confirmed cards also include Shadow-Aldius, Amethysnake, Swordoll (all purple spirits), Viking-Leiv, Wild-Horn (white spirits), Pure Elixir (Revival) (white magic), and No. 1 North Sea Road (white nexus). His battle record shows losses to Yukimura in episode 15 and to Dairokuten Maou in episode 36.

The character draws inspiration from the historical Sengoku-period commander Shibata Katsuie, known for his fierce loyalty to Oda Nobunaga and his "Demon Shibata" epithet. A reprinted magic card titled "Phase Change" features his character art, though this is not a unique card exclusive to him.