There are several mangas that share similarities with Kamisama Kiss. For example, 'Fruits Basket' has a touch of fantasy and romance like Kamisama Kiss.
One common theme could be magic and its use. Since 'Charmed' is about witches, fanfics might explore different magical abilities or spells. Another theme could be family bonds, as the Halliwell sisters in 'Charmed' have a strong family connection. And perhaps the theme of good vs. evil, which is central to the show, might also be explored in these fanfics.
It usually features intense emotional connections and romantic storylines between male characters. The art style might be detailed and visually appealing.
The Kamisama Kiss manga is fully complete. It has covered everything the author wanted to convey, giving a comprehensive and fulfilling story. There are no loose ends or unresolved issues, making it a well-rounded manga series.
One possible scenario in such a fanfiction could be Nanami and Tomoe going on a journey to the spirit world together. They might face various challenges there, like dealing with mischievous spirits. Tomoe, with his powerful yokai abilities, would protect Nanami throughout the adventure. And Nanami, with her kind heart, could end up making friends with some of the spirits they encounter.
In a Tomoe x Nanami fanfiction, it would be interesting to write about a situation where they have to pretend to be a married couple for some spirit - world related reason. They would have to deal with all the implications of that, like sharing living quarters and acting affectionate in public. This would force them to confront their true feelings for each other.
There might be some fanfiction on FanFiction.net as well. However, the quality can vary greatly. Look for stories with high ratings and reviews. Some authors are really good at exploring the concept of Nanami being pregnant in the context of the Kamisama Kiss universe, adding new plotlines and character developments.