This game cg is from a game called "Quilt." That's why it had the tag in the first place.
Want proof? Go to the following link, and click on the "character" button on the top menu. You'll see this character, named Mizuki (I don't know if she has a last name) in the list.
Perhaps I should have added a wiki page earlier for the tag, but clicking on it would have revealed a set of game cgs from that game, which should have helped you discern the tag's purpose.
Furthermore, this character (along with Sia from the game) seems to have been designed by an artist named Sugiyama Gensho, but I'm not sure a new tag should be started for an artist who isn't popular at the moment.