I'm not entirely sure as there could be multiple main characters depending on the specific volume or arc. But typically, there are characters with strong personalities and unique abilities, like a character who might have some sort of superhuman strength or a special power related to the mind.
The main characters in 'jojo light novel' are often complex individuals. They may have both positive and negative traits. There could be a brooding anti - hero type of character who is initially seen as a bit of an outcast but later proves to be crucial in the fight against the main antagonist. There might also be a more traditional heroic character with noble intentions, but who also has his own flaws and internal struggles.
Often, there are characters from different generations or families in 'jojo light novel'. Some of them could be on a quest for revenge or trying to protect something important. For instance, a young protagonist might be seeking to avenge the death of a family member and in the process, discovers his own hidden powers and allies with other interesting characters.