008Zulu posted...
This is really good! What's the source for it?
If you mean the characters and series, it's Oscar Franois de Jarjayes and Marie Antoinette from the classic anime The Rose of Versailles. It's the oldest anime I've ever watched (released in 1979) and one of my top 20 favorite anime of all time even despite its age.
If you mean the source of the artwork itself, you can use https://saucenao.com/ to find it because linking directly to the source on Pixiv is a bad idea considering how much NSFW content the site has.