Shirakawa Yuni from "Magical Girl Yuni Defeat!", a game by doujin developer C-Laboratory.
Now in Illustrious, with an actual activation tag, and more words on the prompt.
When I looked on my dataset I was like "I don't think I need to add more pictures here." Then I got the game again and did exactly the thing I said I wasn't going to do lol.
Old Description: I didn't even knew she had Shirakawa in her name. Was looking for some pictures I because I was too lazy to redownload her game and danbooru gave me the answer.