Coo Ritter is a black cat familiar partnered with the knight Shimaki Hyou. Their working relationship focuses on combating threats to the planet. Coo Ritter speaks in a quiet tone, frequently ending sentences with "~nano," which contributes to his polite demeanor. His personality is supportive, and he readily assists Shimaki Hyou when opportunities arise. Within the Beast Knights group, comprising other familiar-knight pairs, Coo Ritter operates alongside his partner. His specific combat role, abilities, background story, and character development across official media are not detailed.