The Third Hokage's training might have introduced Naruto to more advanced jutsus. For example, he could have taught Naruto better control over his chakra, which is crucial for performing ninjutsu. This would allow Naruto to use his Rasengan more effectively and with less strain.
One challenge could be mastering difficult jutsus. The Third Hokage might set high standards for Naruto to learn complex techniques, which would be a struggle for him.
It could be an older version of Orochimaru who has also found a way to time travel. He might try to change the past to his advantage, like getting rid of the Third Hokage before he can become a threat to his future plans. Orochimaru is always power - hungry and his older self could be even more dangerous with knowledge of the future.
He would likely be seen as a traitor by the village. The villagers, who once saw Naruto as a hero - in - the - making, would now turn against him. He'd be hunted by the ninja forces of Konoha.
A possible plot is that the Third Hokage travels back to when he first became Hokage. He realizes all the mistakes he made in his first term and gets a second chance to do things right. He could focus more on training the younger generation, like Naruto and Sasuke's predecessors, in a better way. He could also be more proactive in dealing with external threats and internal conflicts, which would have a huge impact on the future of Konoha.
Well, it could be that the Sexy Jutsu has some sort of psychological effect on the Third Hokage. Maybe it reminds him of someone or something from his past that makes him hesitate. And in that moment of hesitation, Naruto is able to use the distraction to his advantage and defeat the Third Hokage. Also, Naruto might be able to use the jutsu in combination with other moves in the fanfiction. For instance, while the Third Hokage is distracted by the Sexy Jutsu, Naruto quickly follows up with a Rasengan.
One way this could be developed is if Naruto is somehow mind - controlled. For example, an enemy uses a powerful genjutsu on Naruto, making him lose his sense of self and see the Third Hokage as a threat to the village instead of a protector. Then, in his confused state, he attacks and kills the Third Hokage. This would create a huge moral and emotional conflict within the story, not only for Naruto when he comes to his senses but also for the entire village.
Sasuke could be an alternative. He has strong ninja skills and a deep understanding of the ninja world. His experiences have made him grow into a very capable person, and his Sharingan gives him an edge in combat and strategic planning.
Well, it depends on the specific fanfiction. Some fanfictions might explore alternate storylines where Naruto doesn't become the Hokage at all. Maybe he decides to pursue a different path in life, like focusing on being a teacher or an explorer. However, in a large number of fanfictions, he does achieve his goal of becoming the Hokage because it's such an iconic and desired outcome for fans who want to see his journey to the top in different ways.
Friendship is a common theme. Enma and Tsuna often form a strong bond that helps them through difficult situations. They support each other and learn from one another.