One idea could be that Naruto and his friends are transported into the Minecraft world. They have to learn how to use Minecraft's resources and mechanics to get back home. They might face challenges like fighting off Minecraft mobs that are much more powerful in this new world.
In a Roblox x Minecraft fanfic, the plot could be centered around a competition. The best builders from Roblox and Minecraft are pitted against each other. They have to build a grand structure within a set time limit. However, as they start building, they realize that there are some common threats in both worlds that they need to deal with first, like a horde of zombies in Minecraft and some evil robots in Roblox. So, they decide to work together to fend off these threats before resuming the competition.
Another interesting concept is that the chakra in Naruto is related to the energy in Minecraft. Characters from Naruto have to learn how to use Minecraft elements to control their chakra better. For example, they might meditate near Minecraft's redstone to enhance their chakra flow. And in return, Minecraft characters learn ninjutsu from Naruto and his comrades to protect their world from new threats.
A great plot could be an OC who is a trader that has a secret map leading to a long - lost treasure in the Minecraft Diaries world. They team up with the main characters to find it, facing many obstacles like mobs and rival traders along the way. The OC could have a special ability to communicate with certain mobs which helps them on their journey.
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.
One idea could be that a zombie virus spreads in the Naruto world. Naruto and his friends have to not only fight the zombies but also figure out how the virus started. Maybe Orochimaru was experimenting with dark jutsu and it went wrong.