Sayonara no asa ni yakusoku no hana o kazarô

This is a high fantasy film set among a people with very long lifespans. At the beginning of the movie, the Elder tells Maquia that if she ever meets someone from the outside, she must never fall in love, otherwise she will learn true pain. (Due to the difference in lifespan)

It pretty much seems like a set up for a tale of forbidden romance. She will probably meet a man from the outside. Instead, after their home is attacked (and presumably destroyed), she escapes and finds a baby whose parents were killed. She takes the baby in and decides to raise it. The movie is about her struggle trying to be a mother. Eventually, as her adopted son out-ages her, it creates heartbreaking friction between them.

It was a different choice from the movie to focus on a parent-child relationship in this context. Sure, a star crossed romance would have been Romantically tragic, but shifting the focus to a story where you have a child and you know you are going to outlive the child by a lot ... that is its own kind of heartbreak that we don't often see be the heart of such stories.