Potentially IS a creep depending on why he is interested. Of course its hard to truly know a person to pass proper judgment. Indeed its an extremely complex situation. Even if his thoughts are pure, he's still presumably capable of being intimate with a child-like human being which is very concerning. Her disability essentially robs her of any potential sexual relations and her ability to reproduce. Though I would assume she's not physically able to give birth anyway since her body apparently never matured pass year 8.