I love this series, but I would probably like it more without all the isekai fantasy world stuff. The real treat is the reverse-isekai stuff with Mary learning about the human world and Japanese/human culture. And it'd be nice if they went from all the tentative sort-of-flirting to an actual relationship, but that obviously won't happen because as much as the tag gets used, most shonen manga are allergic to actual relationships when instead they can just drag out the teasing and near-misses until the audience gets sick of it.