How do you know that that's Sakuya (and even more: Chen) in the picture?
The pixiv post is tagged as "original", no chen or izayoi/sakuya taggings, not even touhou. There is only this comment: あ、マスターが咲夜さん似なのはサークル側の設定です。 As I don't speak Japanese, I guess (babelfish), that "master" looks similar to Sakuya. So I think, that this original character (master ?) is supposed to look like Sakuya (similar to), but you can't tell that nekomata is Chen.