This chapter 796 exposed that Kyros was a prince from a far away Kingdom, but then he ended up saying that it was a lie. But I think that he was telling the truth and that he is from alabasta. That's why he might leave and join the strawhats, to fulfill his sisters role without him knowing it. The major reason for this theory is that he looks exactly like Nefertari Cobra....
Nefertari Kyros ?
Nefertari Kyros ?