What's the link between Joy Boy and the Lunarians?
Gorosei spoke of a specific and maybe special fruit, presumably Gomu Gomu (for the moment we will call it that, even if we know that this is not its real name). Kaido's words in chapter 1042 would have already underlined how "special" Gomu Gomu appeared.
This means that Luffy has more skills than rubber specific ones. For example, let's think of another skill that Luffy can use. We all remember Red Hawk and Red Rock:
... it seems that Luffy can control flames. Which reminds us of a race known for this ability: King's race, Lunaria.
Marco said: "fire conjuring race that lived on top of the Red Line". And also Queen: "they were all supposed to be eradicated" and "they were considered gods"
We can thus summarize the characteristics of the Lunaria race: 1 – they can manipulate flames; 2 – people considered them as gods; 3 – they were supposed to be extinct; 4 – they lived on the Red Line.
Now let's consider Who's Who's words about Nika:
Actually, we don't have enough information about the Sun God but we could try to hypothesize Nika's characteristics:
1 – as we said, Luffy is able to manipulate flames and this ability could come from Nika himself; 2 – we know that, according to legend, he was considered the "Sun God"; 3 – his identity is hidden by the World Government to the point that the man who told Who's Who about Nika has been taken away... it’s been said that Lunarian race is extinct but it may actually have been "wiped out" from the World Government. During the fight between Zoro and King, we see a man saying:
4 – why was Nika called "SUN God"? Perhaps because he was able to manipulate flames, or because, if he had been Lunarian, he too would have lived on the Red Line, which is objectively close to the sun.
We now know that Joy Boy/Nika has awakened in Luffy's body. So, most likely, Nika also has the skills of a rubber "human being". And this seems to be another skill that Nika would have in common with Lunarians. Let's look at this technique from King, which probably made us smile:
King seems to be "rubbery". Could we say that Luffy ate a fruit that gives him characteristics similar to those possessed by the Lunaria race?
What we know is that Lunarians have black, feathered wings, brown skin, and white hair. And that the Strawhats already met a race with wings on their backs: the Shandia, the inhabitants of Shandora, during the Skypiea arc. We know that there were four tribes: Skypieans, possessing small wings that are pointed upward; Shandians, who possess wings that also point upward; Birkans, with wings pointed downward. In the Enel's Great Space Operations Cover Page Serial, it was revealed that all the three tribes once lived on the Moon. When they exhausted the resources of their land, they came to Earth and settled on Skypeia and the nearby Birka. "Luna" is the Latin word for "moon", and considering the Lunarians also have wings, it is hard to not see a connection with the other "moon tribes".
In chapter 1035, King finally revealed his face, which he usually keeps hidden under a mask to hide his Lunarian identity from the World Government. When this happened, we could see that he bears a striking resemblance to Wiper, a character that the Strawhats encountered during the Sky Island arc. Wiper had features similar to King's, and the two also share a peculiar tattoo around their left eye. This could be yet another sign of shared heritage between the Shandian and Lunarian tribes. Perhaps the Lunarians were the ruling tribe on the Moon.
Let's go back to the Sun God Nika: the word "Nike" in Greek means "victory", and in the Javanese language victory is "Jaya". An ancient, legendary king from Java was called Joyoboyo, which sounds a lot like Joy Boy. Joyoboyo was a strong and wise king, who brought prosperity to his kingdom. Joy Boy was the "Sun God" of ancient times, and probably the king of the Ancient Kingdom who fought and lost against the World Government. Perhaps the Lunarians were allies of the Ancient Kingdom and were hunted down for this reason. Perhaps they also have a connection to the sun, an idea that is reinforced by their ability to manipulate flames. Perhaps the Lunarians are precisely the Ancient Kingdom people.
We have already connected Nika the Sun God to Skypiea, noticing how the only representation of Nika shown until now strongly resembles a Shandian warrior, and also looks similar to an image of Luffy dancing around a fire during the Sky Island arc.
We now know for sure that Nika is somehow in Luffy. The same person who rang the golden bell in Skypiea and the same who may have been the wise king who brought prosperity to his kingdom.
On the other hand, the cover of volume 27 has always intrigued me... Luffy with a pair of wings throwing us a half moon shaped wink ;)
