As Caiman fights Holey, now a sorcerer, we see that his magic is basically Gyoza magic. It is quite absurd, but it highlights how wacky the series can be. In his heart, Caiman loves Gyoza, and this turns the epic final battle into something more lighthearted. Which it stays true to itself as the series is both cruel and scary but fun and hilarious at the same time.
Though there is a part where Caiman is alongside Chidaruma and they play the lives of the early stages of humans and sorcerers. Simply put, the hatred that Holey has for sorcerers stems from them beating and experimenting on humans. From the beginning of the series, Caiman hated sorcerers and wanted to kill all of them. Now here he has a justified reason to, but he still aims to save Nikaidou, who is a sorcerer. For Caiman it doesn’t matter about sorcerers or humans; his friendship with Nikaidou is irreplaceable.
It makes sense that Caiman wouldn’t be a human zombie for Holey because he has always been immune to magic. Still, it took Shin coming back to be able to take out the devil tumor. It makes sense that Holey has one because Holey comprises the hatred of sorcerers, which he received from Kai. In reality, Holey encompasses the suffering those humans felt. Thus, Caiman just needs to end that suffering once and for all. Remember that humans have been victims of sorcerers for so long.
All that is well ends well. Nikaidou and Caiman have their own shop together. Ai, Aikawa, and Kai live inside Caiman. Funny enough, he accepts himself for who he is. En’s family is back together, but En lost his memories of Nikaidou. It’s a bit odd they erase that memory rather than addressing it.
Chidaruma loses his bet to sorcerers and lives as a human for the next 5000 years. Chidaruma is a being that lived to satisfy his curiosity. While he did lose the bet, I doubt it means much, and this is a new adventure for him. Chidaruma is the character that showcases having absolute power is not as ideal, as he is just curious of what lower lifeforms are like. He is not really a villain in this series but a spectator. He simply wants to be entertained, but you shouldn’t get in the way of his entertainment, as we see many times with him and Asu.