A common theme is the exploration of their relationship dynamic. Given their different backgrounds - Yelena from the Red Room and Kate as a self - made archer - hero, there's often a contrast and then a coming - together. Another theme is friendship evolving into love. They start as comrades or even reluctant allies and then develop deeper feelings.
You can also check out Tumblr. There are often fanfiction snippets and links shared by fans. Some of the fanfictions might focus on their different personalities - Yelena's more brash and Kate's determination - and how they complement each other. They could be in a modern - day setting where they meet in a coffee shop and start off on the wrong foot but then slowly fall in love.
Another theme is the exploration of their individual traumas. Kate has her own set of issues from her past, and Yelena as well. Fanfictions sometimes show how they help each other heal and grow from those past traumas.
There's a fanfic titled 'Unexpected Allies' which shows Kate and Yelena in a different light. They start off as rivals but end up realizing they have more in common than they thought. It has some really cool action scenes and great character development for both of them.
Another interesting one is 'With Yelena by Your Side'. In this fanfic, the author does an excellent job of creating tension and chemistry between Yelena and the reader. It's full of action - packed scenes that also contribute to their growing bond.
Love and romance are also likely themes. Writers may depict the development of romantic feelings between Yelena and Pieck. This could involve slow - burn romances where they gradually realize their feelings for each other, or perhaps more fast - paced love stories where they fall in love quickly due to some extraordinary circumstances. There could also be themes of sacrifice, where one of them is willing to sacrifice something for the other in the context of their relationship.
The relationship development between Yelena and the reader needs to be well - paced. It can't be too rushed. A slow - burn where they gradually get to know each other, like sharing secrets or having small adventures together, makes for a more engaging read. Also, the setting can play an important role. If it's set in the Marvel universe, getting the details of that world right adds to the authenticity of the fanfic.
In many Yelena Belova x Reader fanfictions, the theme of redemption can be found. Maybe Yelena has a dark past and the reader helps her come to terms with it and become a better person. Also, the theme of discovery is quite popular. The reader discovers Yelena's true self beneath her tough exterior, and they form a deep connection. There are also stories that revolve around the theme of family, where the reader and Yelena create their own little family unit in a way.
Well, you can try searching on fanfiction platforms like Archive of Our Own. There might be some great 'yelena x pieck fanfic' there. Just use the search function and type in the relevant tags.