Well, in fanfiction, it could be that Sasuke is the main character who gets involved with the mega buster. He might be on a quest to either obtain it or destroy it because it poses a threat to his goals. Another possibility is that a completely original character is the main focus. This character could be an outcast ninja who discovers the mega buster and uses it to try and find their place in the Naruto world. They might face opposition from the established ninja villages who are either afraid of the power or want it for themselves.
I don't know for sure as it's a fanfiction. It could be Naruto himself using the mega buster. Or it could be a new character created specifically for this story.
Since it's a fan - made story, the main characters could be a group of young ninjas who stumble upon the mega buster. They then have to figure out what it is and how to use it without getting into too much trouble. It could also be that an older, more experienced ninja is the main character and they see the mega buster as a way to pass on their knowledge and skills to the next generation. There are so many possibilities when it comes to fanfiction characters.
Chapter 295, ", Teasing, and the Million Army!", is the clearest early answer because it turns Million Army's situation into a concrete plot event. The setup is Galaraldo could certainly see that Gu Hang now despised him to the..., but the pressure keeps building through But he was all too accustomed to this feeling..
Chapter 424, ", Don't Expect to Reap Without Sowing!", is the clearest early answer because it turns Emerald Spring's situation into a concrete plot event. It opens with Addressing the Green Skin invasion on the various planets within the... and closes on In the star system, they discovered approximately six or seven Green....
Chapter 495, ", Deadly Blood Fight", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter gives readers a real answer by opening on This isn't holding back or deliberately not using the most familiar... and ending on He surely had more than twenty rockets in his two Rocket Nests—how....
Chapter 398, ", Just Like Students of Our Youthful Days", is the clearest early answer because it turns Alliance's situation into a concrete plot event. The chapter turns that into something concrete by moving from He did not miss the opportunity to change his fate; during his school... to What comes next is of utmost importance!" "What should we do?!" "We....
Chapter 349, ", Killed, Bring the Head Back", is the clearest early answer because the violence around Governor becomes final instead of hypothetical. A useful checkpoint is the way the scene starts with Upon hearing the potentially subversive speech delivered by Hu De at... and follows through with It's a pity that the large amount of weapons and equipment he....
Chapter 429, ", Battle Moon", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter gives readers a real answer by opening on After the Mechanical Sect Fleet had departed, Wu Jiarong herself was... and ending on Hope for victory was near, and naturally, they were happy.. In story terms, the danger stops being abstract and the conflict around Yunluo Fleet becomes immediate, forcing the surrounding cast to react under pressure.
Chapter 429, ", Battle Moon", is the clearest early answer because the buildup finally cashes out in a real clash. Early on, The Planetary Defense Force of Frost Origin IV had been consolidated;.... By the end, They had tried their hardest, but the real differences made the.... Inside the broader faction conflict storyline, the danger stops being abstract and the conflict around faction conflict becomes immediate, forcing the surrounding cast to react under pressure.
Chapter 329, ", Heijian Star Joins the Alliance", is the clearest early answer because a shaky connection becomes usable in the plot. The chapter turns that into something concrete by moving from Galaraldo really left a big surprise for both Tianma Star Sector and... to Voyagers', up to now, were not something the Alliance could mass....
Chapter 393, ", Hongjian Star Joins", is the clearest early answer because it turns Pei Desi's situation into a concrete plot event. Early on, Though Flying Wing Star only has a population of eight billion, the.... By the end, This, in turn, amused Gu Hang.. Inside the broader faction conflict storyline, the chapter closes with Off to sleep again..., which gives Pei Desi a stronger narrative position and pushes the power growth onward.
Chapter 458, ", How Dare You?", is the clearest early answer because it turns Alliance's situation into a concrete plot event. The setup is Lalin Ulrich's expression was quite grim., but the pressure keeps building through As a Planetary Governor, and especially as the governor of a small,.... Once the chapter lands on Moreover, a per capita output of 1 tax currency, many planets..., the chapter closes with But at least, the system tried to guarantee fairness as much as possible.