Earthchild

Earthchild is a Manga/Manhwa/Manhua in (English/Raw) language, Manga series, english chapters have been translated and you can read them here.
The Summary is

A regular person falls in love with a superhero who protects Earth! In terms of circumstances, ability, experience–they are from two different worlds, but they get to know each other, support each other, and then… A unique love story on a planetary scale now begins!