Maybe it tickles me because of the anime it is based on. The male character in that scene is a character in an anime that is about as naive as male anime characters in romantic comedyish animes can possibly be. You know the type, ones where a guy happens to be holding a pair of panties, a girl walks in, screams, hits the guy, runs out crying, and then say, "I wonder what that was all about..."
As for human standards, he is probably emotionally 9 years old (18 years old in male anime character years), and the female in that scene is explaining in the most simple blatent terms exactly how to fuck her. And you can see she is quivvering in anger, frustration, and embarassment.
Think about it from her point of view. You've got to fuck this guy(for unspecified reasons) so you are angry. And you know you gotta explain the process to him as though you were talking to a child, so you are both frustrated and terribly embarassed. I'm probably reading too much into it, but from my point of view, it is fuckin' hilarious.
