User blog comment:Xilinoc/Ch. 612 - DIRTY/@comment-24384892-20150122223349/@comment-1268838-20150122224115

It's just a style quirk that Kubo is fond of. That is, ending chapters with something happening in media res, before elaborating on the moments leading up to that moment in the following chapter. I'll be the first to admit that it can be unnecessary at times, but I think it's a good way to build suspense.