Katsunishiki is Akari Unryu's champion sumo wrestling pig.
Katsunishiki is the latest in a line of champion sumo wrestling pigs raised by the Unryu family. Currently the 14th yokozuna, he has held this title since Akari was a young girl. Katsunishiki is mostly light coloured but has a few spots. He wears the mark of the yokozuna's rank, the white tsuna, around his neck over a dark keshō-mawashi. He is quite large, being taller than a human, and is very strong. Highly intelligent, he understands Akari's commands and is utterly devoted to her, serving as her guardian and personal mode of transportation.
Akari's grandfather had declared that she could not consider any man until he had defeated Katsunishiki, and since she was a young girl Akari had tested numerous young men against the yokozuna. However they had all fallen to him until one day, when Katsunishiki was rampaging through Furinkan and had attacked several of Ranma Saotome's classmates, including Hiroshi and Daisuke. When Akari saw Ryoga Hibiki fighting Ranma on the street after school, she had Katsunishiki attack. Ryoga pulled out his umbrella to quickly sent the pig skyward and dropped a banana peel that Ranma slipped on, causing Katsunishiki to fall on him. Being the first man to defeat Katsunishiki, Akari was instantly infatuated with him.
When Akari later visits Ryoga at his home, Katsunishiki punches a hole in a wall to gain entry. After Akane Tendo also arrives and Ryoga is running back and forth between her and Akari, Ranma disguises Katsunishiki as Akane, but even Ryoga does not fall for this shallow disguise. While Katsunishiki is a manga-only character, in Ryoga, Run Into the Sunset, a bull named Gertie has several attributes that are similar to Katsunishiki.