[hide][/hide]So Jinbe needs to go on a diet first? rimshot /terriblejoke
But seriously, I figure I'll weigh in here (*rimsho– SHUT UP!). Wow, I'm on fire. Ok, first thing, what happened in this chapter was predicted by many of us here, almost perfectly. From the gag-intro of Luffy being mad at Jinbe declining, to Luffy's persistance, to Jinbe having some "duty" holding him back, to some further foreshadowed past exploration (scar, anyone?). We have our answer, we just need to know the "what" and "when"?
The obvious answer to the "what" question of duty is his former crew, given they have yet to enter the story outside of flashback, namely Aladdin, and they aren't allowed on the island. It may be more than that, or something else entirely, but we have nothing really to base it on and the previous crew is still a loose end, so not much to discuss there except that if it comes up now, it will be resolved before we leave Fishman Island. But see, that's the only area that is really tugging at me. "IF it comes up now" suggests the crew might return at some point later, or we– via world building-- might return to Fishman Island while the crew is elsewhere. So that brings us to the question of...
When? I can't shake the feeling Oda is laying the ground work for either a continuation of this arc, meaning another issue comes up before the crew leaves, or that Oda is planning for the crew (or the readers) to return at some later time. Aside from Jinbe's duty and yet-to-be-explored more-recent past, we also have the Council of Kings, the slave trade, the World Nobles, Caribou's stolen treasure, and most importantly the Shirahoshi/JoyBoy legend. The latter suggests that Luffy or someone else will return at some point and lead or guide Shirahoshi and Noah, and given the Noah needs repairs... I don't know, it could easily go either way, but of course I have trouble imagining the crew returning to Fishman Island before near-series end, and we currently have two loose ends that would better be handled now than later-- The Fishman Pirates and Caribou.
Anyway, this situation with Jinbe is clearly different than Vivi's, and not because of simple semantics, but because of their respective "duty". Vivi's duty to her country is unending. She doesn't, or rather won't, lose her status as Princess and later Queen. Jinbe, on the other hand, has duty that can and will be resolved. Again, the question is simply a matter of "when"?
I think I might close this thread and start a new one since, well, the Jinbe debate will go on a little longer, but those of us arguing for him more or less had our argument validated by the simple act of Luffy asking him and him indirectly accepting the proposal. Though not technically "right" yet, I need nothing more, myself.