One idea could be a crossover where Naruto's world is in danger and he somehow gets transported to Weiss's world. There, he has to team up with Weiss to fight a common enemy. Maybe a powerful dark mage that threatens both their universes. Another plot could involve Weiss learning Naruto's ninja techniques and incorporating them into her combat style, creating a unique fighting style that surprises their friends and foes alike.
A possible plot is that Naruto and Weiss meet during a magical tournament that has some sort of interdimensional participation. They initially clash due to their different ways of approaching combat - Naruto's more impulsive ninja style and Weiss's more refined and calculated magical attacks. But as they get to know each other, they start to respect and learn from one another. For example, Naruto could teach Weiss about the power of friendship and determination in a more direct and passionate way, while Weiss could show Naruto how to better strategize his attacks.
Perhaps in this fanfiction, Weiss discovers a strange portal and steps through it, ending up in the Naruto world. She meets Naruto and is intrigued by his ninja abilities. They could start training together, with Weiss learning some ninja techniques and Naruto learning about Dust. Their combined skills could then be used to protect Konoha from a new threat that has some similarities to the Grimm from her world.
One idea could be that Naruto and Weiss are both summoned to a strange dimension. They initially don't trust each other due to their different backgrounds. But as they face various challenges like powerful monsters, they start to learn from each other's skills. Naruto teaches Weiss about his chakra control and shadow clones, while Weiss shows Naruto how to use Dust magic. Eventually, they become friends and find a way to return to their respective worlds.
Maybe they get transported to an alternate universe where they are the only two people who remember their original world. They have to rely on each other to survive and find a way back home. Along the way, they learn things about each other that they never knew before, like Ruby's hidden insecurities and Weiss's dreams for the future. This journey could bring them closer together.
Another plot could involve their friends' reactions. Yang could be overprotective, while Blake might offer more calm and practical advice. The story could focus on how their relationships with their friends change as they prepare for the babies. They might also have to deal with the expectations of their families.
A plot could revolve around Sesshomaru being intrigued by Naruto's determination. Sesshomaru decides to train Naruto in some of his own combat techniques, which Naruto adapts to his own fighting style. In return, Naruto shows Sesshomaru the value of friendship and loyalty within a village. This could lead to Sesshomaru having a change of heart about his own solitary ways. Also, they could team up to face a common foe from Sesshomaru's world that has somehow entered the Naruto universe.
One idea could be that Naruto and Kashuina meet during a mission outside of Konoha. They start off as rivals, constantly trying to outdo each other in combat skills. But as they face various challenges together, they gradually develop a mutual respect and then deeper feelings. Another plot could be set in a post - war scenario where Naruto, now a hero, meets Kashuina who has a unique ability to heal the psychological scars of the war - torn ninjas. Their interaction then leads to a romantic relationship. And a third idea is that they are both students under a new sensei who pairs them up for special training. During this training, they discover things about each other that they never knew before and fall in love.
One idea could be Naruto being sent to the world of Death Note. He could use his ninja skills to try and outwit Light Yagami. Maybe he would initially be confused by the Death Note's power but then use his determination to stop Light from his killing spree. Another plot could involve Naruto meeting the Shinigami. He might learn about the balance between life and death in this new context and try to find a way to bring some of his ninja world's values to this strange new world.
Perhaps Naruto and Lala meet during a mission where Naruto is sent to a different dimension. Lala, being from an alien world, is intrigued by Naruto's determination and they form an alliance to face a common enemy in that dimension. Their different powers and abilities complement each other, and as they work together, they start to develop feelings for each other.
A more complex plot could be that there is a prophecy in both worlds about a union between someone from the Naruto universe and someone from Ruby's universe. Naruto and Ruby are the ones fated to fulfill this prophecy. They initially don't get along but as they face various challenges together, they start to understand each other and fall in love, while also saving both their worlds in the process.
In a naruto x avatar fanfiction, there could be a scenario where the Akatsuki from Naruto's world teams up with some of the villains from the Avatar world. This would force Naruto and the Avatar (whichever one it may be) to put aside their differences and form an alliance with other characters from both worlds to stop this powerful and evil coalition.