"Devil fruits are real," Luffy interrupted, touching his necklace at the question, its purple gemstone resting comfortably against his chest.
"What?" Zoro asked incredulously.
The teenager in the straw hat smiled sarcastically at his friend's astonished expression. "Devil's fruit exists," he repeated. "I almost ate one as a kid, but..."
Zoro continued to stare at the boy with some disbelief, still not quite believing him, "But what?"
"Secret," Luffy replied with a mocking smile.
Ignoring that for the moment, the verdet continued his questioning: "So, you ate a devil fruit and that's why your skin looks as hard as metal... And that black thing is part of it too?"
"No, I haven't eaten a Devil Fruit; if I had, I wouldn't know how to swim. Shanks told me so," she said, her gaze distant. She gently untangled the necklace and smiled as if remembering something happy.
At this, Zoro was even more confused. If it wasn't a Devil Fruit, which he'd just discovered was real if he believed his future captain, what on earth was it? Besides, why did he feel like he'd heard the name Shanks before?... "So...? What? Is it magic? Did they experiment on you?" Zoro asked, exasperated. What else could it be? Normal humans couldn't do those things! At least he couldn't... Right? The laughter that escaped Luffy's lips only irritated Zoro more as he patiently awaited the young man's answer.
After controlling his laughter, Luffy answered, and although it wasn't the answer Zoro was hoping for, it was enough to satisfy the swordsman, for now.
"Sorry, Zoro, but for some reason, those assumptions amused me greatly," he began, still chuckling slightly at the scowling young man. Looking at Zoro, he knew he wouldn't be talking to him about Haki just yet. Luffy wanted him to discover it on his own. Not only was he certain Zoro could do it, but he also wasn't entirely sure he could teach it properly. After all, he was only sixteen. If the concept were easy to grasp, surely more people would know about it, and consequently, more people would know how to teach it.
However, such people were few and far between, and Luffy wasn't one of them. He could probably explain how it felt to use it, but explaining how to summon Haki, especially for the first time, was another story. Despite all the training he'd received in Weapon Enhancement and Haki in general over the years, Luffy had only had about four months of actual instruction. Moreover, most of that time was spent learning to control his Conqueror's Haki. It turned out that seven-year-olds didn't learn very quickly, especially when their teacher loved to tease them.
With Shanks it was different; he understood Haki in a way Luffy simply didn't. The man only had time to explain the basics of enhancements; everything else Luffy had figured out on his own. If he knew as much solid information about Haki as Shanks, he didn't think he'd have any trouble teaching Zoro. But in the end, he didn't.
However, that didn't mean I couldn't help him get on the right track.
"The reason my skin is so hard and what appeared on my fist are the same thing, but at the same time, they're not," Luffy declared, contradictorily. Before Zoro could interrupt, Luffy raised his hand to stop him and began to invoke the hardening of his knuckles. Soon, the familiar sensation washed over him: his skin changed from its usual peach color to a dull, blackish gray. He immediately noticed the strain it was already putting on his stamina. It seemed he had more swimming ahead of him... Much more... Also, from what he remembered, Shanks's Haki looked darker. Strange...
Zoro's eyes immediately went to the black substance in Luffy's hand, his question forgotten for the moment.
"This power is something anyone can learn, Zoro, and I hope you learn it too. I think you'll need it if you plan on becoming the world's greatest swordsman," said the boy with the straw hat. The swordsman tried to interrupt him again, but Luffy stopped him once more: "Before you ask, I'm not going to teach it to you. As much as I'd like to, I think it would be better if you figured it out on your own. If you still want me to teach it by the time we leave for the Grandline, I'll try to show it to you. Is that alright with you?"
If Zoro hadn't already been baffled by the news that he too could use the mysterious power, he would undoubtedly have been perplexed by the way Luffy had just spoken. In fact, for once, he had sounded intelligent. "If I can use this power, whatever it is... I don't know if I'd want your help. I think you're right. It's better if I learn it on my own. My own path to strength," the swordsman replied after recovering from his surprise.
Luffy could only smile at his first mate's attitude. He knew he'd chosen a great person for his crew! "Well, now that it's decided... ZORO, I'M BORED!" the straw-hatted teenager shouted childishly.
When the checkmark returned, Zoro decided not to respond and instead lay down for a nap, trying to figure out where to begin learning the mysterious new power he had just been told about.
"I SEE IT! ZORO! I SEE IT!" Luffy shouted from his position on top of Levi's head.
Zoro woke up abruptly, wiping the grogginess from his eyes, "Luffy... If I open my eyes completely, and there isn't an island in front of me, I'll find some way to pierce that skin of yours and-"
"SHUT UP AND WATCH!" interrupted the younger boy. "OH MY GOD, I CAN'T WAIT! LEVI! FASTER!" shouted the black-haired boy happily, completely ignoring the other passenger on the boat.
Just as Zoro stood up to survey the island they were about to reach, Levi leaped forward, following his master's command. The green warrior's feet nearly slipped, but he was quick enough to use his sword to steady himself. "What the hell, Luffy! I could have fallen!" he tried to shout through the wind in his face.
Slowly, Zoro managed to reach the bow of the boat and look ahead in the direction they were heading. Sure enough, an island with a long, curved beach was rapidly approaching. Just beyond the water's edge, a street seemed to stretch along the entire shoreline. Seeing further was difficult at that distance, but from what he could see, it appeared to be the outermost part of a city that grew denser as it extended inland.
As the party drew near, Luffy asked Levi to stop. Zoro had warned him not to scare people, and that was the last thing he wanted. "Alright, buddy, I think we'll part ways here for a while, again," Luffy smiled at his friend. Levi lowered his head so Luffy could climb back into the boat, and once safely aboard, the boy turned to say goodbye. "See you in a bit, buddy," he said affectionately.
The sea beast pushed its nose towards its master's face, stroking him before emitting what sounded like a deep purr and diving down to explore the waters of the East Blue that it had not yet seen.