>a picture of a womans ass that was drawn as fanservice for why there needs to be sex
Also yes, this is called being a male and why giant-ass industry of doujins exists. Men looking at nice character ass and looking for natural continuation, sex, in doujins and the like - is normal. Masturbating - is normal. Am I supposed to be ashamed that my PP gets hard when I see naked Seras ass? Should I be apologizing?

Of course not. Such expectations are healthy and normal for males. If there's a heinous enemy - the story is expected to deliver him to justice. If there's a mystery - it's expected to be unveiled. An unexplored ruin - explored. A nice piece of scantily-clad orbiting love interest - is expected to be fucked by protagonist.

You can do nothing to convince me that there is anything unnatural at all with these expectations.

If you see Seras and not think of sex, there is something wrong with you.