One common theme is the exploration of different worlds. Since Kagome comes from one world and the Kamisama Kiss characters are from another, fanfics often focus on her experiencing the new world of Kamisama Kiss.
Well, 'Kagome in the Kami Realm' is also a notable one. In this fanfiction, Kagome is brought to the Kami Realm from her own world. Her presence disrupts the normal order a bit, and she has to find her place. The way the author describes her relationships with the characters from Kamisama Kiss, like Tomoe, is really engaging. There are a lot of emotional moments as well as some action - packed sequences that make it a great read.
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.
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.
One great fanfiction idea could be that Nanami and Tomoe go on a journey to the spirit world to solve a mystery that threatens the human world. Along the way, they face various challenges that test their relationship and their individual powers.
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 great Kamisama Kiss Mature fanfiction could be the one that focuses on the deeper emotional bond between Nanami and Tomoe as they face more complex challenges in their relationship. It might explore how they grow and change in a more mature way compared to the original story.
One common theme is the exploration of Nanami's relationship with Tomoe. When she is pregnant, it often adds a new layer of complexity to their relationship. For example, Tomoe might become more protective.
You can start by looking on popular fanfiction websites such as Archive of Our Own (AO3). It has a large collection of fanfictions, and you can use the search function to specifically look for Kamisama Kiss Mature fanfiction.