I'm not sure specifically as there could be many different interpretations in this fanfiction. It might be about Naruto having some connection to a character named Lightning Farron, perhaps in an alternate universe where Naruto's origin or abilities are related to this new element of 'Lightning Farron'.
There are often fanfictions where Naruto and Farron form an unlikely friendship. In these stories, they might start off not getting along due to their different backgrounds. Naruto from the Hidden Leaf and Farron from her own world. But as the story progresses, they learn from each other and grow stronger together. For example, Naruto could teach Farron about the importance of never giving up, while Farron might show Naruto some new combat techniques from her world.
Obviously Naruto is one of the main characters since it's in the title. And Lightning Farron is likely to be a main character too, as Naruto is supposed to be his son in this fanfiction. There may also be other Naruto - universe characters like Kakashi or Jiraiya who could play important roles in the story.
First, you need to have a clear idea of the story you want to tell. Decide if it's going to be an adventure, a friendship - building story, or a romance. For example, if it's an adventure, think about the quest they will go on and what kind of challenges they'll face.
One of the appealing aspects of including Lightning Farron in RWBY fanfiction is the potential for crossovers. Writers can explore how the technology and magic of her world interact with the Grimm - filled world of RWBY. It also allows for character development for both Lightning and the RWBY characters as they face new challenges together.
One common theme is identity. Since she's in a crossover situation, Lightning often has to re - evaluate who she is in the new context. For example, in crossovers with other fantasy worlds, she might question her role as a warrior.
One great Lightning Farron crossover fanfiction is 'Lightning in Another World'. It has an interesting plot where Lightning is transported to a different universe and has to adapt to new challenges. The story does a great job of keeping her character true to the original while also exploring new relationships.
Lightning Farron might also fit into the story by being a mysterious outsider. The RWBY characters could be initially suspicious of her, but as they get to know her, she becomes an important part of their group. She could introduce new concepts from her own world, like different types of weapons or fighting styles.
One idea could be that Dark Lightning Farron discovers a hidden power within himself during a great battle. This new power changes the course of the war he is involved in.