Perhaps in the fanfiction, the Lion King 2 characters could be given Naruto - like powers. Simba's daughter Kiara could learn to use chakra and perform ninjutsu. This would change the dynamics of her relationship with Kovu. Their story of uniting the two prides could be enhanced with these new powers. She could use her newfound abilities to bring the two groups together more easily, with the help of Naruto - style teamwork and training.
In a Naruto - Lion King 2 fanfiction, the themes of both could be merged. The idea of destiny, which is strong in both Naruto and The Lion King 2, could be a central point. Naruto's journey to become Hokage is about fulfilling his destiny, just as Kiara's journey is about fulfilling her role as the one to unite the prides. The fanfiction could explore how characters from both universes help each other understand and achieve their destinies, while also dealing with the cultural differences between the ninja world and the Pride Lands.
One way they can be combined is by having Naruto characters in the Pride Lands setting of The Lion King 2. For example, Naruto could be a new kind of 'pride member' with his ninja skills. He could use his shadow clone jutsu to help the lions in battles against enemies, like the Outsiders in The Lion King 2. His positive and determined attitude could also influence the young lion cubs, teaching them about friendship and loyalty in a different way than they already know.