It was this super weird/trippy Japanese animated movie I saw a few years ago. The art style wasn’t typical anime like you tend to see, it was a very unique art style. I don’t remember a lot of the actual plot besides it being about a man who was in love with this woman, I think she might have been about to marry another guy or something. The most memorable scene was later in the movie he finally has sex with the woman he’s in love with and then they (or maybe it was just her) partially transforms into a butterfly (sprouts wings and stuff)/moth/caterpillar. There was a lot of phallic imagery in the movie too. It was the strangest, trippiest movie ever but I remember it being really fascinating too and I wish I could find it!