I got an Ask about the Hugging Illustrations and pre-ordering Volume 23, Volume 24, the third guidebook, and the artbook...
I answered it and clicked the button to privately answer it, but my computer was being dumb and didn't send it, so then I had to refresh the page, and the Ask was gone. I don't know if it got sent properly or not, but here is the response I gave:
Hello! :) There are a variety of hugging illustrations that will come with the pre-orders (1. Oz & Gil, 2. Oz & Alice, 3. Oz & Break, 4. (Oz) + Break & Sharon, and 5. Oz + Elliot + Leo - you get this last one if you pre-order all the items). The Oz & Gil hugging illustration definitely comes with Volume 23, Mochizuki-sensei said this herself on her blog, but I we don't know for certain which of the other hugging illustrations come with what book. If I had to guess though, I would say that Oz & Alice comes with the pre-order of Volume 24, Oz & Break with the pre-order of the Guidebook, and (Oz) + Break and Sharon with the pre-order of the artbook, but that is nothing more than a guess.
At the moment, the only way to pre-order these items is at the PH events (now the PH event at the Osaka Animate), however, I do expect that they will eventually be available for pre-order online (likely after the Osaka Event is over, so at the very end of March/beginning of April). I don't know for certain though if pre-ordering online will definitely come with the hugging illustrations. It has been stated that it is a campaign and that the illustrations will come with your items when you pre-order them at the Animate venues, but there was no mention made of these being special Animate only illustrations. We'll just have to wait and see.
Anyway, I hope this helped clear some things up for you! :D
I hope the asker gets to see this!