So I put the first Daki pillow case I received on my mother's old body pillow, featuring Asuna Yuuki in a frilly pink teddy. 
I followed the enclosed instructions for putting the cover on the pillow, but it was a bit of a struggle rolling up the cover and then rolling it down over the pillow like you're putting on a giant prophylactic, because my pillow is filled with memory foam and is very fat and heavy - but I finally got it on, lol! 
Unfortunately, the body pillow I have is only 54" long, and a standard Daki pillow is 60", so it is 6" short for the covers. I did order a proper 60"x20" (150x50cm) pillow, also filled with memory foam, and just received it today. I haven't put a cover on it yet because it needs to sit and expand for 24-48 hours since it shipped tightly rolled and vacuum compressed.
I posted uncensored images of the reverse side of the pillowcase in the [18+] Hentai Releases thread over in the blu-ray.com anime forum.
Also, I made a mistake in my original post, the second pillowcase I received is not Roxy from Mushoku Tensei, that one is arriving later next week. The one I actually received is Furina de Fontaine from Genshin Impact, and both sides of that one and the Roxy pillowcase are 18+ images.
