Been seeing this cover since late 2016. Japanese. Not sure if it was ever released. Thanks
Artist is Tomohiro kai, he posted the cover on his twitter right after Comiket 91, plus the sketch of a page. Comiket 92 is on August, so expect it to be released then.
If you find this information good, I have a thread up >>15284032 → so if you feel like helping, it would be aprecciated. Have a nice day!