Wait so Ermes and Enya were rock humans? And what's the connection with the stone masks and the arrows?
Edit: So I read some other comments and it seems it was just an example of human females.
The book name is "Poupelle of Chimney Town", there's an animated movie adaptation coming out in December in Japan https://myanimelist.net/anime/35609/Entotsu_Machi_no_Poupelle