I don't remember much about it. It was an old anime or perhaps western animation, most likely anime. All I remember is there was a girl and a fairy boy reminiscent of a moth or butterfly. They would travel trough a forest or some fantasy place.
It’s hard to think of any more details, since I saw it when I was very young. I think I saw it on a VHS tape, dubbed to Spanish around 1998 to 2003.
I think the boy had wings and antenna, and he would carry the girl from one place to another. The genre was fantasy, maybe some romance or friendship thing between the moth and the girl.
The target audience was young children (since the characters were very young).
Other details I can remember (but not sure) is that the characters were at some point standing in a flower or some sort of vegetation, maybe the human girl shrank to insect size. In another scene the girl is sitting near a tree, maybe recalling her times with the moth-boy. Also there was a wood fence like those found in country fields. Like this image below: