Even with a complete lack of plot, there actually was some surprising development this chapter. Like people have been saying, the way he was viewing sex was challenged by the Elder (someone way above his level) and he had to sort of rethink what he was doing and what he was expecting or feeling during it. So his two partners this time weren't fights but reciprocal undertakings and not just concentrating on himself but also each other.
Just a hunch but what if the thing he got from the eldritch and the piano teacher is not really "brainwashing". I think his skills just cleanse him from the romantic feeling that starts building up in his brain.
@kingoffing I can understand the latter, but why would he get romantically attached to the tub lady from the Shining after she put a cigarette out on his forehead?
@Ironclad dunno either, so far nothing really serious have happened and it has been comedic so far, maybe the eldritch woke up his masochistic side? a lot of weird stuff can happen in a manga so I'm just assuming stuff lol