anyone know the story behind this Pieberry costume?

[⎝⧹autarch⧸⎠]

First off, what a great game, I've read quite a few manhwa (korean fan fiction) and felt like I was reading a very good one while playing the game. I think Western storytelling could use a lot more of what they've got in the East.

Because I like the game so much and just for fun, I was looking at some of the game files and I came across this picture of Pieberry in a black dress called 'Pieberry_SeethrougeBlack'. Did I miss seeing this somewhere in the game?
https://i.imgur.com/Eo8KNN7.png

[yolomancer]

I scoured the game pretty good and didn't find it, it may be a part of the upcoming costumes dlc the devs have spoken of