I checked earlier 2013 works to see if this standalone work from his Fanbox/Fantia was already uploaded but I didn't see it or might have missed it. It was an exclusive extra for this work before:
https://e-hentai.org/g/625649/f263831746/

Please support the artist if you enjoy their work!
https://deepvalley.fanbox.cc/posts/2792123
https://fantia.jp/posts/915898
https://www.pixiv.net/en/artworks/37704845
https://www.pixiv.net/en/artworks/93057134

https://www.dlsite.com/maniax/circle/profile/=/maker_id/RG07518.html
https://www.dmm.co.jp/dc/doujin/-/list/=/article=maker/id=24820/
https://twitter.com/deepvalley
https://skeb.jp/@deepvalley
https://pawoo.net/@deepdeep