I don't think she really seems interested in him that way, so he'd probably have to work at it getting her to think of him romantically or even just sexually. She's "18" again now, but was originally 38 so she'd pretty much have to be quite a cradle robber to feel like that about someone who's probably around 15-18. The matter on whether all of that is morally acceptable given her physical age vs mental age is debatable, personally I think being on an entirely different world and having all kinds of supernatural shenanigans in play makes it not really seem like a problem, but the question is how the characters would think about it.