Maybe Darkrai is summoned accidentally by an evil ninja who wants to use its power to take over the Hidden Villages. Naruto, with his unwavering spirit, tries to befriend Darkrai and show it that there is more to the world than just causing fear. This could lead to Darkrai turning against the evil ninja and helping Naruto protect the villages.
In a fanfic, Darkrai could be a part of a prophecy in the Naruto world. It is said that a being from another dimension (Darkrai) will either bring eternal darkness or help in achieving a new level of peace. Naruto, believing in the latter, sets out on a journey to find Darkrai and convince it to side with the forces of good in the Naruto universe.
One idea could be that Darkrai enters the Naruto universe during a major battle. Its dream - inducing powers start to affect both sides, causing chaos. Ninja start to see their worst nightmares, and it becomes a race for Naruto and his friends to figure out how to stop Darkrai and wake everyone up from the nightmarish state.
One interesting plot idea could be that Darkrai and Cressila are from different realms. They meet by chance during a cosmic event that distorts the boundaries between their worlds. They initially see each other as threats but gradually come to understand that they both have a role in maintaining the balance of the greater universe. They team up to fight a common enemy that is causing chaos in both their realms.
One plot idea could be Darkrai's struggle to fit into the Pokemon world of Pokemon Platinum. Since it's often seen as a menacing and mysterious Pokemon, it could be about it trying to prove that it has good intentions. For example, it might try to protect a small village from other powerful Pokemon threats, all while the villagers are initially afraid of it.
The clash of two different universes makes it interesting. Naruto has its ninja world full of jutsus and complex characters, while Darkrai is a mysterious Pokémon. Combining them can lead to unique storylines, like Naruto having to deal with Darkrai's nightmares or using his ninja skills to catch it.
One plot idea could be that Darkrai and Cresselia are forced to work together to save their shared dream realm from a new and powerful dark force. Their initial animosity due to their opposing natures gradually turns into respect and then something more. Another idea is that a spell goes wrong and they swap powers for a while, leading to humorous and also some deeply emotional moments as they try to understand each other's roles better.
An interesting plot idea for Naruto fanfic might be to focus on the life of a minor character. For instance, what if we told the story of a genin who never made it to be a chunin but still had a significant impact on the village in some other way? Or a story where all the ninja abilities are suddenly switched among the characters, and they have to adapt to these new powers while still facing their usual enemies. This could lead to some really fun and unexpected character interactions.
Another plot could be Samui getting involved in a time - travel adventure. Maybe she gets sent back in time to the era when the ninja world was just being formed. She then has to use her modern - day knowledge and skills to survive in that primitive yet dangerous time, and also has the chance to change the course of ninja history in small ways.
One idea could be that Tayuya, after being defeated, has a change of heart and teams up with Naruto to fight a new common enemy. They could learn from each other's skills and jutsu.
One idea could be Shinachiku going on a journey to discover his own unique ninja skills, different from his father Naruto. He could encounter new enemies and make unexpected allies along the way.
One idea could be that Ageha has a special power that only Naruto can help her control. This power might be related to some ancient ninja art. So, they go on a journey together to master it and along the way, they face many enemies and also make new friends.
One interesting plot idea could be a story where the Mizukage and Naruto have to team up to stop a new and powerful enemy that threatens both their villages. Maybe this enemy has a unique jutsu that can disrupt the balance of chakra in the world. Another idea is a fanfic where the Mizukage visits Konoha and Naruto is tasked with showing her around. During this time, they exchange stories about their respective ninja upbringings and learn from each other's experiences. A third plot could involve a time - travel scenario where Naruto goes back in time and meets a younger version of the Mizukage and they end up changing the future of their villages in unexpected ways.