Disclaimer: I don't own One Piece, Eiichiro Oda does.
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Earthborn Dragons
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At one of the many mansions that decorated the Holy Land and capital of the World Government, Marie Jois, a secret training exercise of the Six Powers was being overseen by a young, straw hat-wearing, wingless dragon of all things and also undertaken by a World Noble heirless. Such an occasion was unheard of, but the heirless wanted to learn how to be strong and the agent saw a rare opportunity to influence the Government's politics that a CP-0 agent could only do so much. Thankfully, since the mansion had been closed off since it's former occupants, the Donquixote Family, had abdicated their statuses, no one else was around at the time to witness their training. Otherwise, they both would've faced dire consequences.
"Alright, Saint Shalulia." The grinning agent said to his panting, but none the worse for wear charge. "Now is the time for the ultimate technique." Turning to a nearby boulder, he said. "Just place both of your right in front and let go."
Shalulia nodded, did so, and unleashed a powerful shock wave uttering. "Six Powers Extreme: Six King Gun!"
With it, the boulder was nothing but pebbles. Shalulia gasped for breath, but was able to bow out of respect to her clapping teacher.
"Well done, my Saint." The dragon applauded genuinely even more upon seeing her bow. "For now, we rest. But once you are ready, we will begin working on your Haki."
Shalulia smiled broadly at that as she had been wanting to maximize her willpower from the start of her secret correspondence with her personal spy, martial arts teacher, and lover. "That pleases me, Agent Luffy." She said pridefully, if exhausted.
Taking it as a sign, Luffy picked up a discarded pile of clothes nearby and, after changing into his Human form in front of the unperturbed Shalulia, put them all back on.
"As I said before, Shalulia, I'm not certain you have the rare Haki of a Conqueror, but from our previous exercises, I believe you're more than qualified now to withstand it and use the other forms." He said in a stern voice before showing a warm smile. "Nonetheless, I'm proud of your progress."
Shalulia returned the smile and said. "Any chance I would be able to defeat that pompous fool who used to live here on my own, my darling?"
Luffy chuckled. "That remains to be seen, but if you are successful, I'd be even more proud."
Shalulia turned forward and hummed delightedly. "Rewardingly proud?"
Luffy's smile turned more teasingly. "Well, that depends. What kind of reward were you thinking?"
Shalulia answered with a kiss on the lips. "I was thinking of a few things we could do behind closed doors, my little dragon."
Luffy held her in his arms, and said. "I'm listening, my Celestial Dragoness."
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A bit out of character, I know, but I couldn't think of what other pairing I could've used Kozuki Momonosuke's Artificial Devil Fruit for when HeiseiGoji91 asked. Still, giving the typical World Noble attitude, I suppose I wouldn't be surprised if there was at least one World Noble who wanted to be strong on their own two feet, as Kagetaka showed in their story, One Fell Out Of The Dragon's Nest. Perhaps this would be something an official Cipher Pol agent, or just Government-affiliated, version of Luffy would do in their spare time; make normally weak characters stronger in the hopes they will improve as people as well. I guess I'll see what I can do.