Their relationship could start with Uta being initially distrustful of Luffy. After all, Luffy is a pirate and Uta has her own ideas about pirates. But as she sees Luffy's pure heart and his determination to protect his friends and pursue his dreams, she starts to warm up to him. They might then become friends who share their different stories and experiences.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fan - made stories, and you're likely to find some great 'uta x luffy fanfic' there.
Some 'uta x luffy fanfic' could explore a scenario where Uta joins the Straw Hat crew. This would bring a new dynamic as her musical powers and her connection to Luffy would add interesting plotlines. For example, she could use her music to enhance the crew's morale during tough battles.
There could be a luffy x uta fanfic where they meet in a different timeline. Uta's singing might have a special effect on Luffy, giving him new powers or a different perspective on his goals. This would lead to an interesting exploration of their relationship and how it affects the world around them.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics from various fandoms, including One Piece, so there's a good chance you'll find some luffy x uta fanfic there.
In a fanfiction, Uta and Luffy could team up to discover a long - lost island that is said to hold the key to a powerful and ancient musical instrument. This instrument has the ability to control the sea itself. Along the way, they face many challenges and their different outlooks on life - Uta's more artistic and emotional one, and Luffy's straightforward and goal - driven one - clash and then blend as they learn from each other.
I would recommend 'Uta's Hidden Affection'. In this fanfiction, the development of the relationship between Uta and the reader is really interesting. It starts with small interactions that gradually build into something deeper. The description of Uta's character is very accurate to his original personality in the source material.
Since I can't promote or assume the nature of 'lemon' fanfics which usually contain inappropriate content, if we consider just general fanfics about Uta and Kaneki, they might focus on their unique personalities. Uta is mysterious and Kaneki has his complex journey of self - discovery. Their interactions in fanfics could be centered around their different views on the world of ghouls.
A lot of these fanfictions also explore the idea of self - discovery. The reader character might discover new things about themselves while interacting with Uta. And sometimes, there are themes related to the power of friendship. Uta and the reader might support each other through difficult times, which shows the strength of their bond.
Another option is Wattpad. There are quite a few writers on Wattpad who write uta x reader fanfiction. However, the quality can vary quite a bit. But it's still worth checking out. You might come across some really interesting and unique stories that you won't find anywhere else.