This is a filler for the conversation Luffy and Zoro were having in episode 604. I assumed Nami explained for a few minutes before Usopp and Chopper joined Luffy and Zoro(giving Luffy and Zoro time to have a heart to heart). This is my take on Luffy's inner struggle with all the changes and Zoro helping him through.
"How far did you fly Zoro?"
Zoro took in a deep breath as he moved to beside his captain. Taking in the fresh scent of grass, hint of oranges, rich smell of wood, and the familiar laughter and jostling behind him, Zoro relaxed in a way he'd never relaxed during the past two years.
"Well… Far enough I guess. But I'm back," Zoro answered ruefully; their adventures would be saved for a cold night high up in the crow's nest. Instead, the swordsman leaned his head into his right hand as he sized Luffy up. He came to a decision fairly quickly. "But you're worried about that?"
The darkness that suddenly flashed through the brown eyes did not go unnoticed; Zoro had been expecting this from the moment they met.
"I'm suddenly not sure," Luffy turned to gaze at the murky waters before them. There was a slight shake in the words, the faintest trace of the fragile child beneath the facade of a grown man. Not for the first time, Zoro wanted to ruffle the black hair and assure him that none of them would leave him like Ace did. But Zoro didn't for they were no longer children who yearned for words of confort. They were men.
And more importantly, they were pirates.
So instead, the swordsman straightened up and shifted so their shoulders were touching. The movement was so small, so slight that it would have been unperceivable to the watching eye. However the raven head teen knew and accepted the strength it offered.
"You're right. This is what I want."
The falter was gone.
"But the whole world is after me because of what I did when Ace…died."
Yet the fear remained.
Luffy turned again to look at his friend, and Zoro was glad that there was no regret in the brown eyes. Luffy would do it again for his brother if he had the chance-and Zoro would have it no other way as well. However, Luffy had understood the burden that lay on his shoulders after enduring it alone for two years.
"I don't want to burden you guys as well. It's mine; Monkey D. Luffy, the little brother of Ace's, and the four hundred million bounty pirate's."
Zoro was dimly aware of the shouts and cries of joy from his crew mates coming from behind him, but they held no real meaning to him. He simply focused on Luffy's insecurity that had bubbled up after meeting them-or maybe, Zoro realized, the insecurity had bubbled up because Luffy met them.
Luffy had yet still healed from the pain of losing a loved one and was not ready to accept even the possibility of it happening again. However, as long as Luffy had ones he loved close by like how he did now, he was in danger of the despair that had once clutched his heart.
"I've been waiting for this day for two years. I never gave up and I came this far," Luffy flexed his hand as he continued softly. "To make sure I'd never have to lose you guys again. But I don't want you guys to be in unnecessary danger because of what I did or who I am-"
"Don't be an idiot Luffy." Zoro interrupted, bringing a stop to Luffy's self hate. There was no true malice in Zoro's words but they held the same intensity.
When Zoro looked down at his captain, Luffy tensed against the unfaltering gaze but only for a moment; Zoro would never judge him. Thus Luffy relaxed, amazed at how when he was beside Zoro, everything else seemed to slip away. They were no longer several hundred thousand feet under the water. They were back at a Marine headquarters, in a dusty and dry plain, when the two of them first met. And Luffy wasn't the four hundred million berry captain of a fearless crew, or the little brother of Fire Fist Ace. He was a pirate who was excited by his future which he would mold with his own two hands, a pirate who was neither fazed nor daunted by the darker world which had less tolerance to such dreams, and a pirate who recognized the same fierce glint of hope and determination in the green headed swordsman's eyes.
"You think any of us are here for Portgas D. Ace's little brother? Or the Straw Hat pirate worth four hundred million berries?"
He was simply Monkey D. Luffy; nothing more, nothing less.
"We came back, for you."