In this fanfiction's opposite world, the concept of the jinchuriki could be turned on its head. Instead of being seen as vessels of great power that need to be protected and controlled, they are feared and hunted down not for their power, but for some other reason, like they carry a curse that affects the world negatively. And the way ninjas train could be completely different too. Maybe instead of physical and mental training, it's all about some sort of spiritual sacrifice.
One idea could be a modern - day person suddenly being transported into the Naruto world and having to learn chakra control from scratch. They could struggle with the cultural differences and make friends with some of the original characters like Naruto or Sakura while trying to find a way back home.
One idea could be Naruto being a high - school student. He might use his ninja skills secretly to help his friends out of various troubles, like bullies or difficult exams. For example, using his shadow clone jutsu to study for multiple subjects at once.
One idea could be Naruto getting trapped in the demon world and having to form alliances with different demon clans to find his way back. He could learn unique demon jutsus during his time there.
Perhaps in this fanfiction, Naruto is the only man left with chakra. This would make him a target for those who want to control or use his power, leading to intense battles and power struggles.
One interesting plot could be a story where Naruto discovers a hidden ancient jutsu in the fanfiction world that gives him the ability to travel between dimensions. He uses this power to visit alternate versions of Konoha and teams up with different versions of his friends to face a new, powerful enemy that threatens all the dimensions.
One idea could be Naruto arriving in a world full of magic, and he has to learn to combine his chakra skills with magic. For example, he might use his Rasengan with a magical spell to create a super - powerful attack.
One idea could be exploring the darker sides of the ninja villages that are usually hidden. For example, the corruption within the political systems of the villages. Another could be focusing on characters who have turned to the dark side due to past traumas, like a character who lost their family in a war and then joined a dark organization. Maybe also a plot where the traditional ninja values are being twisted in the 'world of darkness' version, leading to moral dilemmas for the main characters.
In some naruto alternate world fanfiction, there could be a plot where Naruto travels back in time. He could use his knowledge of the future to prevent tragedies like the Uchiha massacre. He might also be able to train with the past Hokages earlier and gain different skills. This would change the course of the entire Naruto world, and his relationships with characters like Sasuke and Sakura would be very different as a result.
One idea could be Naruto arriving in a world full of magic. He has to learn to combine his chakra skills with magic to defeat a powerful dark lord. For example, he might use his shadow clone jutsu in creative ways within magical battles.
One idea could be Naruto having to adapt to the different social norms in the female - ninja world. For example, the way training or missions are organized might be different. Maybe the female - ninjas have a more collaborative approach compared to the male - dominated world he's used to.