Well, in fanfiction about Saiki Kusuo and Teruhashi, often their relationship is explored in really interesting ways. Sometimes it shows Teruhashi's attempts to get closer to Saiki in a more comical way compared to the original series. And Saiki, with his unique powers, might react in different and unexpected manners.
Fanfiction on Saiki Kusuo x Teruhashi can vary greatly. Some might focus on the development of their relationship from Teruhashi's perspective. She is often seen as the popular girl who is intrigued by Saiki. Writers may play with the idea of how she tries to break through Saiki's cold exterior and get to know the real him. This can lead to some really cute and funny scenarios.