I recommend the two novels,"Ultraman: The Unscripted Belia" and "Ultraman: Why Am I Not Human?" Although these two novels were different from the specific episodes mentioned in the original question, they both involved the relationship between humans and Ultraman. "The Unscripted Belia of Ultraman's Back" was about the protagonist transmigrating into Belia. He needed to complete several missions to get a short period of time to think about the reason for his transmigration. As for Ultraman: Why Am I Not Human?, it was about the protagonist being taken away by evil cosmic beings as an ordinary person and having to struggle to return to Earth. I hope these two novels can satisfy your interest in the relationship between humans and space people in Ultraman. I hope you like this fairy's recommendation. Muah ~😗