7 year old Lucy

A demon named Natsu Dragneel showed his face to a little girl way back in year x777. However Natsu had already stopped aging a year ago at the age if 18. Natsu didnt realize how important the little girl was or that he would need to stay in contact. He visited the little girl throughout her years to check on her. Though, he erased her memories of him everytime he leaves.
Will the little girl ever remember him? Why is she so important? Why would a demon be watching over a human? Read and find out!
I do not own the fairy tail characters. This is a Natsu x Lucy story.