One interesting plot could be Natsu going back in time to prevent a great disaster that happened in the past of his world. For example, he might try to stop the initial attack of a powerful dark guild that had long - lasting negative impacts. Another plot could involve Natsu traveling back to his own childhood and having to deal with his past self, which could lead to some comical and heartwarming moments as he tries to impart some of his current wisdom.
If Natsu goes back in time, his relationships would be very different. With his friends, he might have a new level of understanding. For example, he could see how they grew up and the challenges they faced in the past. He might be more protective of them, especially if he knows what's going to happen in the future. His relationship with Lucy could also change. He could see her in a new light, perhaps realizing things about her that he didn't before when he first met her in the present.
One common theme is self - discovery. When Natsu goes back in time, he often learns more about himself, his powers, and his past. For example, he might find out things about his family or how he came to be who he is.
Gray is also a popular character to be paired with Natsu in these fanfictions. Their friendly rivalry can take on new dimensions when Natsu travels back in time. They could end up working together in unexpected ways in the past.
If Natsu travels to a time when Fairy Tail was just starting, he would be more eager to prove himself. His competitive side would be even stronger. In a more distant past, like when dragons were still around, he might be more in awe and a bit more reserved as he encounters these powerful and mysterious creatures. In a future where magic has evolved, he could be a bit out of place at first, but then adapt and become more open - minded to new forms of magic.
Some common themes could be time travel adventures. Natsu might go back in time to prevent a disaster in the Fairy Tail world. Another theme could be self - discovery. As he travels back, he learns more about his past and his true potential.
It could be a time - traveling version of Zeref. He might be trying to stop Natsu from changing things in the past that could potentially lead to his own downfall in the future.
It could be Zeref. If Natsu goes back in time, Zeref might have different plans or be in a more powerful position at that time. He could be the main obstacle for Natsu to overcome, especially if Natsu is trying to change things related to the dark magic that Zeref wields.
One interesting plotline could be Natsu going back in time and accidentally changing something that has a huge impact on the future of Fairy Tail. For example, he might prevent a key member from joining the guild, and then he has to figure out how to fix it.
One plot idea could be Natsu traveling back in time to prevent a great disaster that he has knowledge of in the present. For example, he could go back to stop the rise of a powerful dark wizard before they gain too much strength. Another could be Natsu traveling to the past to meet his long - lost family members and learning about his past and heritage. He might also time travel to the future to see how his friends and the guild have changed and use that knowledge to better the present.