Well, in this fanfiction, it might be that Naruto's transformation into the four - tails form reveals some hidden secrets about the Nine - Tails' origin. This could lead to a whole new adventure as he tries to uncover more about it. Also, perhaps the four - tails form has a different set of abilities compared to what we've seen before, which makes for exciting battles and challenges for Naruto to overcome.
The main character is Naruto for sure. But other characters like Jiraiya might play a significant role. Jiraiya could be the one to guide Naruto in controlling the four - tails' power. Also, characters from the Akatsuki might be main antagonists. They would be interested in Naruto's new power and try to capture or use him for their own purposes, like Pain or Itachi.
One idea could be exploring the Four Tails' backstory more in - depth. Maybe it has a connection to an ancient ninja clan that was long forgotten. Another is a story where the host of the Four Tails has to team up with an unexpected ally to control its power.
One interesting plot point could be the reaction of the other Jinchuuriki. Since Naruto now has the power of all the Tailed Beasts combined, the other former Jinchuuriki like Gaara might have mixed feelings. They could be both in awe of Naruto's new power and a bit envious at the same time.
One idea could be exploring the origin of the Ten - Tails in a different light. Maybe it was created by an ancient civilization for a noble purpose that got corrupted over time. Another could be a story where a young ninja discovers a hidden power within the Ten - Tails and has to learn to control it without being consumed by its dark energy.
Well, one interesting plot point could be Ash encountering new and rare Pokémon in Sinnoh that he's never seen before. Maybe he discovers a unique form of a Pokémon that's native to Sinnoh. Another could be his interactions with the Sinnoh gym leaders, like having intense battles or forming unexpected friendships with them.
In 'Deku Goes Berserk' fanfiction, a great plot point might be how the other characters react to Deku's new, wild side. For example, Bakugo could initially see it as a sign of weakness, but later realize it's a powerful force that needs to be harnessed. This could lead to a whole new dynamic between them. Another aspect could be how Deku's transformation affects his relationship with All Might. All Might might worry that he's losing control and try to help him in a different way than before.
One key point could be the initial confrontation. Naruto has to face the Nine - Tails' wrath head - on. This is a dangerous but necessary step as it sets the stage for their relationship. He might get seriously injured in this encounter but also learn a great deal about the Nine - Tails' power and nature.
Another cool plot twist could be that the Ten Tails has the ability to split into multiple smaller entities, each with its own unique power. This would force Naruto and his friends to come up with new strategies to deal with these new threats. And it might also lead to some of these smaller entities turning good and helping Naruto in unexpected ways.
Often, the plot point where Naruto uses his 'player' skills to outwit stronger opponents is really interesting. For example, in some fanfics, he tricks his enemies into believing he is weaker than he actually is.
Well, a common plot point is the culture shock. Naruto comes from a world full of ninjas and chakra, while Najenda is from a more modern - ish world with different forms of combat. Their reactions to each other's worlds can be really interesting. For example, Naruto might be amazed at the technology Najenda has access to, and Najenda could be intrigued by the idea of chakra.