Well, this was honestly one of the best yuris I've read here. In the favorites it goes.
So the wings were symbolic of virginity... or something?
I think?
Maybe?
I don't really know. I know this comic is trying to tell me something, but I'm too dumb to know what that is. It's nice though, I kinda like not knowing exactly what it is.
It reminds me of change and growth in general, but the difference between them is more important than the wings themselves. MC thinks to herself several times that she's "just a normal human", compared to the angel, hence she cannot follow her where her growth is bound to lead her. It distresses her much, that as the angel grows, she risks becoming an ever smaller part of her world.
Of course, life is like that too. Relationships come and go, perhaps your crush will get married, your friends and you will slowly and silently drift away, your children will move out, or your lover will grow distant following their calling. In any case, either the relationship, or part of its significance to you, will be lost.
Doesn't even need a good reason really. People live at different paces, and the slower ones are bound to be left behind by the faster ones if the latters don't slow down for them.
So yeah, progress, growth, change. All of those places most people want to go. They stare at them for days, and even if they can't get there overnight after growing wings, it's still a looming threat if the stakes are high for you. It's insecurity (though not always a misplaced one) at its finest, it can only really be resolved if you have faith in the relationship. Not always possible, but that's what the angel's resolution is for at the end here. "Even if I can go on without you, I won't", basically.
My apologies if this comes off as rambling though!