@AllFine
This is basically "Grooming: The Manga," yeah. That they're already "in a relationship" instead of her waiting isn't really relevant to that fact - the dynamics of the two of them in this manga are honestly about as textbook as it gets as far as this goes. More to the point, that's the end goal there anyway: normalizing the behavior for the one being groomed. In this case, the manga's just started off with the grooming already well underway.
I'm not saying this manga can't exist, not shaming you if it's your thing, whatever, but let's skip beating around the bush and call it what it is.