To add on to what RedAmaranth
has kindly answered above... ^^ As far as I know (no I haven't watched the movie yet... I just have been reading tons of Japanese industry trade reports for the movie, and movie reviews, summaries, and reports, and Japanese blog entries from people who watched the movie in Japan. ^^)
there is no "romance" in the movie. But, we all know Al has a kind soul, right? And, in the movie, Al ends up protecting Julia and saving Julia (couple of times, I think) and ends up physically carrying Julia often
Just warning Al-fangirls
But, as far as I see, there is nothing more than that.
As for the OP song... I believe Miwa's song is of love & romance, but as an OP for the movie, this can be the expression of love by people of Milos for their lost nation, or, if I may say, reading the lyrics makes me think that this could be a song that's expressing family-love/emotions between siblings
... I think you might see what I mean after watching the movie.