Okay, this chapter's ecchi moment felt a lot more honest, cute-hot, and in line with the promise of the story. It had that "experienced girlfriend turns up the charm and makes you feel all melty inside" feeling, plus genuine gratitude and goodwill from the MC making it feel like her goal was to have Senpai enjoy herself. Page 18 = very good page. More of this! More soft and good emotions+affection leading to sexy things that everyone is enjoying! That's what this story needs.
That pretty much is what MC has been going for since the beginning, it just doesnt turn out this well most of the time because (like we have seen in ch1 and a few flashbacks) she is still socially incompetent and ends Up trying to mask it with sexuality because she doesnt know how Else to keep Setos interest enough and is scared of letting her get away again.