Like the manga, disagree with the psych101

Freud is very influential, and his theory of the uncanny, for instance, is one I really like. But just pointing out, many of his theories have been discredited and disputed. His ideas about sexuality and gender, particularly, come from a very different time (the 19th century). Remember, this is the guy who believed that all girls and women suffer from "penis envy," because we all subconsciously know that men are better.
Regarding the afterword, I think it's dangerous to apply such a heteronormative way of thinking to non-heterosexual love/sex, and it runs the risk of being very dismissive. Unlike most other animals, humans are NOT driven only or even mostly by the biological imperative to reproduce. Our social psychology and social lives, including our sexuality, have moved far beyond that. Sex has way more of a social function for us, rather than a biological one. So the idea that a sexuality which can't produce offspring causes psychological angst in and of itself is wrong, and frankly kind of insulting. Just my 2 cents.