Luffy's entire demeanor visibly grew more excited after learning about the Road Poneglyphs.
Originally, his understanding of becoming the Pirate King had been quite simple. He merely thought pirates were the freest "profession" in the world, able to do whatever they wanted, while the Pirate King was the freest person in the world. And Luffy wanted to become the freest person in the world.
He had set sail based only on youthful passion and a longing for freedom.
He had recruited his crewmates based solely on whether they clicked and whether fate had brought them together. As for how exactly to become the Pirate King, Luffy had generally just followed his instincts, taking things one step at a time.
Even so, ever since Luffy had set sail, he had never gone wrong in the overall direction. After weathering some storms and hardships, the Straw Hat Pirates had finally entered the New World, drawing ever closer to the Great Treasure they sought.
And today, Luffy had learned the whereabouts of the Road Poneglyphs from Vivi. This made his goal increasingly clear. To Luffy, becoming the Pirate King had officially changed from an elusive slogan into something tangible.
"Vivi, do you think... we need to make a trip back to Fish-Man Island?"
"Even though we don't know whether the New Marines moved the Road Poneglyph from Fish-Man Island, there's no harm in going there to investigate."
"If the New Marines didn't move that Poneglyph, then wouldn't we..."
Luffy's little brain had finally begun thinking about serious matters. Although he knew that the Road Poneglyph on Fish-Man Island might already have been moved by the New Marines, Luffy still wanted to return and investigate.
At present, of the Poneglyphs they knew about, there were only two locations Luffy clearly knew and recognized.
Fish-Man