This gallery is the official release from DMM: https://www.dmm.co.jp/dc/doujin/-/detail/=/cid=d_658388/ It is different from https://e-hentai.org/g/3488731/2088189f06/ which is just a Fantia/FANBOX compilation.
They key differences include corrected resolution sizes for pages 3, 4, 8, and 9, as well as including the afterword and back cover.
The textless cover is a Fantia/FANBOX exclusive, so it was not included in the actual release. The reason why page 2 and page 31 are omitted in the file names is because for the physical release of the doujin, these pages are actually left completely blank (they're the other sides of the front and back cover).