Redemption is also a common theme. Especially when it comes to Sasuke's character. Some fanfics explore his journey to make up for his past mistakes and how Naruto is there to help him through it. It shows the power of forgiveness and second chances in their relationship.
Another theme is power and growth. Writers often show how Naruto and Sasuke develop their powers in new and different ways in fanfics. They might gain new abilities or train in unique ways to face greater threats. For example, in some fanfics, they learn ancient jutsu together. This not only makes them stronger but also deepens their bond as they rely on each other during the learning process.
One popular theme is friendship. Their relationship is a central focus, and many fanfics explore how they support and understand each other on a deeper level.