One possible plot could be that Naruto accidentally unleashes a much more powerful version of the Katon Gouka Mekkyaku during a training session. This causes a lot of chaos in Konoha. As a result, he has to figure out how to control this new power. He might seek help from his friends like Sasuke or Sakura. They could try different methods, like using medical ninjutsu to balance his chakra or Sasuke's sharingan to analyze the technique better. Meanwhile, there could be some villains who are interested in this new power of Naruto's and try to steal it for their own evil purposes.
Well, the plot could involve Naruto exploring new ways to use the Katon Gouka Mekkyaku. Maybe he's in a battle against a powerful enemy who has some sort of resistance to fire techniques. So, Naruto has to combine it with other jutsus or find a new way to channel the chakra for this technique to make it more effective. He could also be teaching the technique to some of the younger ninjas in Konoha, which would lead to some interesting training scenes and character development for those new ninjas.
The plot might center around the origin of the Katon Gouka Mekkyaku. In the fanfic, it could be revealed that this technique was once used by an ancient and powerful ninja clan. Naruto discovers some hidden secrets about this clan while trying to master the technique better. This could lead him on a journey to find ancient scrolls or talk to old sages who might know more about it. Along the way, he would face various challenges and also learn more about the history of his own village and the ninja world in general.
Chapter 451, "Where Did This Madwoman Come From?", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. It opens with Upon hearing this, the three people turned their heads in unison.
Chapter 364, "This is the gift our master sends you for the first meeting", is the clearest early answer because it turns Shariputras's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The final item is our heavyweight treasure for today." Even the host...
Chapter 242, "Jiang Yan's Dazzling Transformation Journey", is the clearest early answer because it pushes Dazzling Transformation Journey into a new phase or setting. It opens with Just when Jiang Yan called to heaven and earth in vain, he looked up...
Chapter 261, "They've Ruined the Entertainment Industry!", is the clearest early answer because it turns Shu Yan's situation into a concrete plot event. Early on, The village chief's eyes nearly popped out after he heard the whole.... By the end, Is it necessary to be so guarded against me?.
Chapter 568, "Not at All", is the clearest early answer because it turns All Shang Shaojing's situation into a concrete plot event.
Chapter 732, "Sister Xiao Wan, I Don't Understand", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. The chapter gives readers a real answer by opening on Bai Lu, eavesdropping in the corner, marveled at Jiang Cheng's...
Chapter 306, "I Believe Whatever Miss Jiang Says!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter turns that into something concrete by moving from But Jiang Li seriously shook her head, "No, Aunt Zhou, this matter...
Chapter 397, "Talent Show Program", is the clearest early answer because it turns Youth Trainee's situation into a concrete plot event. The chapter turns that into something concrete by moving from Second Aunt, I know you're worried about Shixu interacting with...
Chapter 600, "You merchants aren't even fit to carry my shoes!", is the clearest early answer because it turns Jin Siyue's situation into a concrete plot event. The chapter turns that into something concrete by moving from Shen Ruobing was not deaf to the ironic tone in Jin Siyue's comments,...
Chapter 445, "Mysterious Creature Appears!", is the clearest early answer because it turns Yu Zhongyi's situation into a concrete plot event.