Described by Toriko as the most powerful of the "Four Heavenly Kings" for his pure destructive capabilities, Zebra is a very large and well-built man with scars that cover most of his body, one of the more striking ones being the half Glasgow smile on the left side of his face. His personality is very angry and small-tempered, he enjoys fighting the most out of all the Heavenly Kings and has a self-professed hatred for anyone or anything acting "cocky". He is incredibly strong, and until recently, he was held in "Honey Prison" for eating 26 species of beasts to the point of extinction. He and the other Four Heavenly Kings were trained by Ichiryū, the president of the IGO. Zebra has the power to both hear and send out ultrasonic waves, as well as the ability to hear even the faintest sounds from tens of kilometers away.

Hajime Saitou is loosely based on the real third-squad captain of the Shinsengumi. During the Meiji era, he lived as a police officer under the name of Gorou Fujita. In the Rurouni Kenshin series, he plays the role of Kenshin's old rival and enemy from the Bakumatsu. He has no compassion or mercy for his enemies and he lives by the Shinsengumi code "Aku Soku Zan (悪即斬)," literally "Slay Evil Immediately," but more poetically rendered as "Swift Death To Evil." His signature technique is the Gatotsu, a left-handed thrust and a variation of the Hirazuki technique developed by Toshizou Hijikata, the Vice Commander of the Shinsengumi. Although the Gatotsu is a fictional technique only found within the Rurouni Kenshin series, the Hirazuki is a real technique that was used by many of the Shinsengumi members.