The Monkey King — Challenge!
One Piece x Naruto Crossover
The Chthonic Professor
Premise: The Third Hokage is disappointed in how Naruto is acting in relation to his performance in school. Naruto whines about the fact that the other students get unfair treatment, because most of them are from clans and have prior training and help at home. Though this is in part the reason they receive preferential treatment, Sarutobi also knows it's because Naruto is the container of the nine-tailed fox.
In a stroke of inspiration, Sarutobi finds a way to deal kill two birds with one stone. He's been so busy with his duty as the leader of the Leaf, that Enma, his summon partner, has gotten rather bored lately. Because he personally doesn't have the time to train Naruto, Sarutobi tells Naruto that if he can summon Enma, then the monkey will teach him, curing both of his problems at once.
He allows Naruto to summon the Monkey contract (silently asking for Jiraiya's forgiveness), and teaches Naruto the hands signs for the technique. Though he was originally planning on staying until Naruto was able to summon one of the smaller Monkeys, and then summon Enma himself, one of his advisors comes rushing into the training ground claiming there's been a crisis. The Third rushes off, telling Naruto not to try summoning anything while he's gone.
Naruto, of course, doesn't listen. He stays out in the sun all day trying to summon something, with no results. Just as the sun begins to set, he gets fed up and accidentally draws on a minute amount of the Nine-Tails' chakra. What he summons, however, isn't Enma, but a young man, no older than eighteen.
The young, happy man introduces himself as Monkey D. Luffy, Sage of the Monkeys. Naruto explains that he wants to become stronger to prove that he's the best ninja in the Hidden Leaf, and become the Hokage, Luffy takes a liking to him, and promises Naruto that he'll turn him into the strongest ninja the Leaf Village has ever seen.
From then on out, Luffy takes it upon himself to personally take care of and train Naruto. He has no need to return to the summoning world because he's a human, and (though unintentionally), he hides himself from everyone Naruto knows, training him in secret.
The year before Naruto's graduation, Luffy tells Naruto that he has to go away on a trip, explaining it's personal business. In actuality, Luffy is going out to search for a devil fruit to give to Naruto, for when he graduates.
I'd prefer it if he was given the Flame-Flame fruit, as the power of the fruit could be amplified by the Fox's natural powers of foxfire.
Side Note: The reason for Luffy being the Sage of the Monkeys is not actually because of his name, but because of his Devil Fruit ability. I watched a theory on Youtube involving the fact that Luffy's 5th Gear transformation could possibly be into the Monkey King Sun Wukong (related to the awakening of a Paramecia Fruit's powers and the fact that 4th Gear has to do with a gorilla).
Like Luffy's 5th Gear Awakening Transformation into the Monkey King, Naruto could eventually have a Fusion Transformation of sorts with Kurama, where when fused together they become a fox-related God of Fire, or something.
On the topic of Kurama, I'd also prefer it if the story followed Canon only in the sense that it ends with a massive colossal fight between Madara and the Ten Tails vs. Naruto and Luffy. Whatever else you do with the story is entirely up to you. This is just an idea for the people of fan fiction to use.
Also, if any ideas spawn from my own, and you want to write them, be my guest. I will never be one to withhold creative inspiration.
If anyone's willing to take on this challenge, I only ask that you PM me when it comes out, so that I may read it. Because I sowant to read a story about this.
Anyway, The Chthonic Professor, signing out.
Peace!