The combination of two very different universes. Naruto is from a world of ninjas, chakra, and hidden villages, while Diavolo is from a different kind of fictional world. When these two worlds collide in fanfic, it creates a unique and exciting setting.
Sukuna does die in the manga. The way it happens is quite dramatic and ties in with many other elements of the story, adding depth and tension to the overall narrative.
A great 'naruto diavolo fanfic' to check out is 'Naruto Meets Diavolo: A Crossover of Worlds'. It delves deep into the characters' personalities. Naruto's determination and Diavolo's leadership are put to the test as they navigate a world full of political intrigue and dangerous enemies that span across both their original storylines.
Overall, Sukuna's portrayal in Fuga manga is quite compelling. The artist does a great job of showing their power and personality through detailed illustrations and storylines. However, there are some moments where the character's development could have been a bit more fleshed out.