Let me explain. On pixiv the chapter are regroup by 14 to 22 pages and actually the last one of the 1st grouping is chapter 5 not chapter 3, that explain why it end strangely here. We are indeed up to Chapter 11 on Mangadex which is the first half of the 3rd grouping of chapters on Pixiv. Just for you know, there is 17 grouping of chapters on Pixiv for the moment, which give more than 70 chapters i believe if you go by 4 pages.
Oh, the backstories are definitely not fun, lol... I've seen up to around chapter 11 translated and so far that hasn't revealed too much. I mean Kaede's is kinda obvious but her mistress' is not. But we're given some subtle hints, like how she refers to using her money, so I'm thinking whatever happened to her she's either being given financial restitution or her family is paying her off to be quiet about whatever it was.