Despite the focus being on sex early on, this series develops honest to goodness storylines and plots that are unironically interesting later on. The mystery going on in the latest volumes is pretty page-turning. Unlike some other manga which might have done better as just regular h-manga, I can see why this is presented as a normal, if more ero-y manga. The sex is just one aspect of the story, not the main focus, like with actual hentai manga.