One possible plot could be that Naruto discovers Fem Kami in a unique situation, like she's lost in the human world. He helps her adapt and during this process, they grow close and eventually fall in love. Their marriage could be a grand event, uniting the ninja world with the divine realm in a symbolic way.
In this fanfiction, Fem Kami could be a key to saving the ninja world from a new, powerful threat. Naruto teams up with her, and during their adventures, they realize their feelings for each other are more than just friendship. The marriage then becomes a celebration of their victory over evil and the start of a new era of peace and harmony between different realms.
Perhaps Fem Kami has been observing Naruto for a long time and decides to take on a human form to be closer to him. Naruto, at first, is a bit skeptical but as he gets to know her true self, he falls for her kindness and beauty. Their marriage might face some opposition from traditionalists who don't believe in such a union between a ninja and a deity, but they overcome it through their strong bond.