The Fire Carp was in fact merely a carp. He was called the Fire Carp because his body was red from head to tail like the fire and he lived in the fire source.
He was indeed a lifeform of the divine animal; otherwise, he wouldn't have lived for tens of thousands of years and was still not an adult. As such, he called himself the King of the Fire Carps.
In fact, he was still a child.
He appeared to be cowardly and was inclined to bully the weak and afraid of the strong. He was very talkative, and his expression was often naïve. This was because he had lived in the underground for tens of thousands of years and hadn't met many humans. Though he hadn't communicated with many people, he was in no way stupid.