It just feels like Oda is just trying to fit so much into this backstory, that it feels like nothing is happening. I'm not feeling any connection with any of the characters, i'm just waiting to see the black borders fade back to white. It doesn't help that Oda has not focused on ANY of the Straw Hats since the jump. We have seen one, maybe two attacks from each of the straw hats, but all that served to do is show how they've become a ton stronger.
And why is Otohime so important that we need what probably totals an issue now of her just being a diplomat? I think a page explaining that she wanted mermen and human beings to live together would have sufficed.