One way is to put them in a situation where they have to live in a different realm for a while. They'd be out of their comfort zones and would have to depend on one another. This could include things like finding food, shelter, and making new friends in this strange place, all while growing closer.
Their relationship can be developed by having them face challenges together. For example, dealing with a difficult spirit that only they can handle as a team. This would force them to communicate better and trust each other more.
Another approach is to introduce a character who is interested in either Jirou or Nanami romantically. This would create jealousy and make them realize their true feelings for each other. They would then have to fight for their relationship and in the process, it would become deeper and more meaningful.
One plot idea could be Jirou and Nanami getting lost in a magical forest together. They'd have to rely on each other to find their way out, facing various magical creatures along the way. This would test their relationship and maybe lead to some romantic moments as they huddle together for safety at night.
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.
Another way is by showing their vulnerability around each other. In some fanfictions, Tomoe, who is usually strong and stoic, shows his weaknesses to Nanami. And Nanami, in turn, is able to comfort him. This mutual trust and the ability to be vulnerable in front of one another is a big step in developing their relationship further.
You can start by looking on popular fanfiction websites like 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 fanfictions related to Nanami and Tomoe.
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.
One way to develop their relationship further is to put them in a completely new environment, like a small island where they are cut off from the fashion world for a while. Here, they would have to rely on each other in a more basic way. They would learn new things about each other, like how George is really bad at fishing but tries hard for Yukari, and how Yukari discovers she can cook simple but delicious meals for George. This would strengthen their bond on a more personal level.
After the kiss, they could start secretly dating. Strange might use his magic to create private, romantic getaways for them, away from the prying eyes of the other Avengers or the magical community.
One great place to find kamisama kiss kurama x nanami fanfiction is on Archive of Our Own (AO3). There are many talented writers who create interesting stories about them. Some might focus on their budding relationship, while others could explore different scenarios like them going on adventures together.