This manga has 33 chapters total (far as I can tell), and MangaDex has them all, but the numbering is completely off for the first 12.
What complicates this is that MangaDex's chapters 1, 2, and 3 have 6 pages each - 3 chapters each.
This means these 9 chapters are incorrectly reducing the total count in the table of contents (they are also out of order).
If these 9 are separated out, then there will be 33 chapters, 3 more than on Dynasty. The chapters 31, 32, and 33 on here (starting with the Christmas party invite) are placed correctly at the end.
The order of chapters seems correct over on Dynasty, meaning the proper chapter 1 should be the one with the bathroom stall and follow from there.