One popular Tory and Robby fanfiction could be about their adventures together in a martial arts tournament. Maybe they team up against a common rival and their relationship deepens through the challenges they face.
You can try fanfiction websites such as Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, so there's a good chance you'll find Tory and Robby fanfiction there.
One great Robby and Tory fanfiction is 'Robby and Tory's New Beginning' which explores their relationship as they train together and overcome challenges. It shows their growth as characters.
One common theme is friendship. They often start as friends or rivals and then develop a deeper bond. For example, in many fanfics, they first compete in some activity and then realize they have more in common than they thought.
One popular storyline could be Robby and Tory teaming up to face a common enemy within the karate world. Maybe an old rival from another dojo who has a vendetta against Cobra Kai. They put aside their differences and use their combined skills to protect their dojo.
A great 'tory x robby fanfic' that I've come across is 'The Hidden Feelings'. It starts with a rather tense situation between them and then gradually unfolds their true emotions for each other in a very engaging manner.
In some fanfiction, Robby might develop by becoming more confident in his abilities. For example, if he's in a story where he has to lead a group of younger students, he could grow into a more responsible and self - assured person. Tory, on the other hand, could develop her softer side. Maybe she befriends someone outside of karate who helps her show more compassion.
One common theme is redemption. Given his complex backstory in the show, many fanfictions explore his journey towards redemption. They might have him making amends for past mistakes and becoming a better person.
Love is a very common theme. Most fanfictions explore the romantic relationship between Acheron and Tory, showing how they fall in love and overcome obstacles in their relationship.