The tag of Dark_Takao_(Azur_Lane) refers to a version of Takao_(Azur_Lane) that appears in the game, but never in the game is she called that. Instead, she's called Ember or Code T in comments by the artist.
This actually has precedence in the Dark Enterprise character that is usually tagged as Code_G_(Azur_Lane) as that's how she's known as in the game. In fact, Code G is also her pixiv tag.