Another interesting aspect could be femto Naruto's impact on the ninja world. Since he would be different in this form, he might introduce new jutsu or ways of thinking. He could inspire younger ninjas to think outside the box and break traditional boundaries in their training and combat.
Start with a strong opening scene that grabs the reader's attention. It could be a fight scene where femto Naruto shows off his new powers in an unexpected way. Then, gradually introduce the backstory and the details of his femto form. Build up the story slowly, adding more elements like character relationships, conflicts, and how the ninja world reacts to this new version of Naruto.
Guts is purely fictional. It's a concept or character that exists within the realm of imagination and creative storytelling rather than being based on reality.
Perhaps in this fanfic, Griffith has turned into something truly evil and a threat to the world Guts cares about. Guts, being the warrior he is, might feel it's his duty to put an end to Griffith to save others. Also, Guts could be driven by his own sense of justice. If Griffith has wronged innocent people, Guts may decide that killing him is the only way to set things right.