Their relationship in the fanfiction is likely to be full of mutual understanding. Since they are getting married, they must have a deep connection. Takato might be the more gentle and patient one, while Rika could be the strong - willed partner. They balance each other out.
Maki in fanfiction usually has a fierce loyalty to her friends, especially Yuta. She is the type to fight for what she believes in. Yuta is sometimes portrayed as being a bit naive in the ways of the world outside his own small circle, but his pure heart makes him endearing. In many stories, their different personalities create an interesting dynamic, like in a story where Maki's boldness gets them into a risky situation and Yuta's calm thinking gets them out.
In many Geto and Gojo fanfictions, the theme of trust is crucial. Their trust in each other can be tested in various ways. Another common theme is the exploration of their past. What made them who they are? How did their past experiences shape their relationship? And the theme of growth, both as individuals and in their relationship with each other, is also often seen.
His relationships, especially with other characters like Gojo, are often explored. Fanfics might show the deep friendship they had before Geto's fall and how it deteriorated. It gives more depth to their dynamic.