One common theme could be friendship. Maybe the fanfics explore how mutsumi and kae's friendship develops over time. Another theme might be adventure, with them going on some exciting journey together.
I'm sorry I don't have specific mutsumi x kae fanfic to recommend directly. You could try searching on fanfiction websites like Archive of Our Own. There are often many fan - created stories for various pairings, and you might be able to find some great mutsumi x kae fanfics there.
They could start a secret project together, like creating a hidden garden on school grounds. As they work on it in secrecy, they share secrets and dreams, which deepens their bond.
Yes, there are some. You can start by checking fanfiction websites like Archive of Our Own. There might be various stories exploring the relationship between Kae and Mutsumi in the 'kiss him not me' universe.
One common theme is the development of their relationship. Writers often explore how Mutsumi and Kae gradually get closer and understand each other better.
Overcoming insecurities is also a frequent theme. Both Shima and Kae might have their own insecurities, whether it's about their appearance, popularity, or how they fit into each other's lives. Fanfiction writers often delve into how they support each other and overcome these insecurities together, which can be really heart - warming and a great exploration of the characters' personalities.
Some smaller, niche fanfiction communities or forums dedicated to 'kiss him not me' might also be a good source. These can be a bit harder to find, but if you search on Google using phrases like 'kiss him not me shima x kae fanfiction community', you might stumble upon some places where fans gather to share their works. Keep in mind that these smaller communities may have their own rules and regulations regarding fanfiction sharing.
Another option is Tumblr. There are many anime fans on Tumblr who create and share fanfictions. Use relevant tags like '#KissHimNotMe', '#Mutsumi', '#Kae' and '#MutsumiKae' to narrow down your search for the fanfiction you're interested in.
One idea could be that Nanashima and Kae go on a school trip together. During the trip, they get separated from the group and have to rely on each other. This forces them to face their feelings for each other more directly. Another plot could involve a misunderstanding. Maybe Kae thinks Nanashima likes someone else, and Nanashima has to find a creative way to show her that he's actually into her. For example, he could write her a song or create a special art piece just for her.