One possible plot could be that Naruto is somehow transported to the world of Final Fantasy IV. He teams up with Cecil and the others. Naruto's unique ninja skills could be used to help in battles against the various foes in FFIV's world, like the Golbez's minions. His rasengan could be a powerful new attack for the group.
A great plot could involve Naruto being mistaken for a legendary hero in Final Fantasy IV's world. He has to prove himself worthy of this title. Along the way, he learns about the crystals that are so important in FFIV. He uses his shadow clone jutsu to protect the crystals from being stolen by the forces of evil. His friendship with the characters in FFIV grows as they see his determination and selfless acts.
Maybe in this fanfiction, the chakra in Naruto's world is related to the magic in Final Fantasy IV. Naruto discovers that he can use his chakra to enhance the white magic of Rosa. Together, they work on healing the wounded in a war - torn land. Meanwhile, Sasuke, who also gets transported, is tempted by the dark powers in FFIV, similar to Golbez, creating a conflict within the group.
One interesting plot could be that Naruto and his friends somehow get transported to the world of Final Fantasy 15. Naruto's ninja skills would be a huge asset in the new world. He could team up with Noctis and his crew to fight against a common enemy, like a powerful daemon that is causing chaos in both their worlds combined. Maybe Naruto could teach Noctis some of his chakra control techniques in exchange for learning some of the magic from Final Fantasy 15.
Naruto and Cecil would be an interesting pairing. Cecil is a noble knight with a complex past, and Naruto is a determined ninja. Their different backgrounds and fighting styles could lead to some great interactions. Cecil could learn about Naruto's will to never give up, and Naruto could be inspired by Cecil's sense of honor.
In this fanfiction, it could be that there is a prophecy that involves both Lulu and Naruto. The prophecy states that only by combining their powers can they save both their universes from a great evil. So, they meet and at first have communication problems due to their different backgrounds. However, as they train together and share their stories, they form a deep bond and work towards fulfilling the prophecy.
Perhaps in the fanfiction, the Akatsuki organization somehow gets hold of the power to summon Final Fantasy creatures. Naruto then has to figure out how they got this power and stop them. He might have to train hard to master the same summoning techniques. He could end up summoning a Shiva to counter the Akatsuki's Ifrit summon in a huge battle that shakes the very foundations of the ninja world.
It continues the story of 'Final Fantasy IV'. It likely involves the further adventures of the characters from the original game, perhaps exploring new lands, facing new threats, and deepening their relationships.
Well, it could be about Naruto characters getting sucked into the world of Final Fantasy 8. Maybe Naruto could team up with Squall. They'd fight some of the FF8 monsters together, and Naruto could use his jutsus while Squall uses his gunblade. It'd be a really cool mix of the two universes.
In some Naruto x Final Fantasy fanfiction, the summons in Naruto could be related to Final Fantasy summons. Like the toads in Naruto could have a connection to a similar creature from Final Fantasy. This would create unique interactions between the two universes.
Some cool crossovers might include Naruto's summoning jutsu being used in the world of Final Fantasy X - 2. He could summon giant toads or snakes, which would be a strange sight in Spira. The Al Bhed language from Final Fantasy X - 2 could be something Naruto characters have to learn. And perhaps the Farplane in Final Fantasy X - 2 could have a connection to the afterlife in the Naruto universe. This could lead to some really deep and emotional storylines where characters from both worlds interact with the concept of death and the afterlife.
One interesting concept could be the combination of Naruto's ninja abilities with the job classes in Final Fantasy 14. For example, a character from Naruto might take on the role of a Black Mage in FF14, using their chakra in a way similar to how a Black Mage uses mana. Another concept could be the interaction between the different worlds. Maybe the Hidden Villages could exist in the same universe as Eorzea, and there could be diplomatic relations or even battles between the two. Also, the idea of characters from FF14 learning ninja techniques from Naruto characters would be really cool.
It's about the post - events of the original FFIV. Characters like Cecil and Rosa have aged, and they have to deal with new troubles in their world. For example, there are strange happenings that seem related to the moon. It has a lot of callbacks to the original game while also introducing fresh elements like new characters related to the old ones.