Kuro understands Iwanaga's circumstances the most. She was a child when the monsters kidnapped her, took her one eye and chopped one leg to make her a "God". It is not at all an honourable title to be bestowed on, she's a disposable God if she can't serve her purpose anymore. Kuro understood that and feared for her; she disregards her safety because of her disposability, and she's not even scared to be replaced right after. Kuro's powers were given to him solely to protect and help Iwanaga, as he very much believed to be the case. "In sickness and in health" he said. Iwanaga exists to be the God of Wisdom, and Kuro exists to be with her.
Kuro understands Iwanaga's circumstances the most. She was a child when the monsters kidnapped her, took her one eye and chopped one leg to make her a "God". It is not at all an honourable title to be bestowed on, she's a disposable God if she can't serve her purpose anymore. Kuro understood that and feared for her; she disregards her safety because of her disposability, and she's not even scared to be replaced right after. Kuro's powers were given to him solely to protect and help Iwanaga, as he very much believed to be the case. "In sickness and in health" he said. Iwanaga exists to be the God of Wisdom, and Kuro exists to be with her.
Readers would doubt whether or not Kuro truly loves Iwanaga, and I get that, but it's funny to me that Rika think the opposite. To Rika, Iwanaga only uses Kuro for her duty as the God of Wisdom (take note that even Iwanaga could not argue with that). Kuro and Rika's existence ruins the natural order, so it makes sense to kill Rika, to which is what Iwanaga's trying to do throughout the story, but the same applies to Kuro, would it not? Rika thought that Iwanaga would not fear killing or more specifically, sealing both of them, and she's not even scared that she doesn't care at all. What does that say about Iwanaga? "If you have any shred of humanity left in you" Rika cleverly used Kuro against Iwanaga, manipulating her into thinking that she would not care if Kuro disappears as a part of her duty. Rika led her into thinking a scenario where Kuro disappears and guess what? Iwanaga is mortified, thus collaborating with Rika in the end.