I'm not sure specifically as there could be many different stories with that title. It might be about a character or group of characters who break limits in some way, perhaps physical, mental or magical limits within the fictional world of the web novel.
I don't have enough information to determine who the main characters are. It could be a young hero on a quest, or a group of friends with unique abilities.
A 'naruto ssj3 fanfic' is likely a fan - made fictional story that combines elements of Naruto and the Super Saiyan 3 (SSJ3) concept from Dragon Ball. It could be about a Naruto character achieving a form similar to SSJ3, perhaps with new powers and abilities, and the adventures or battles that follow.
One aspect of Vegito and Female Gogeta fanfiction could be the exploration of their unique power combinations. In these fanfictions, writers might create scenarios where they team up against a powerful enemy. For example, they could face a new, extremely strong villain that neither could defeat alone. Their combined strength and different fighting styles would make for an exciting story.
One common theme is power comparison. Writers often explore how Vegito's power from Dragon Ball stacks up against the powers in the other crossover universe, like the magic in a Harry Potter crossover or the quirks in a My Hero Academia crossover.
Maybe it's because Bulma has her own established character traits and relationships in the original story. She might not fit well into the scenarios often presented in Vegito fanfic. Also, her character is more focused on other aspects like her scientific work and family in the canon, so fanfic ideas involving her in a Vegito - related context could seem out of place to her character.
If Vegito never unfused, it might mean that the enemies he faced were simply not strong enough to force the separation. This could imply that the story's difficulty level was lower than originally thought. Or, it could be that some external factor prevented the unfusing, creating a whole new set of plot twists and complications.