gundou mirei (6th costume)
The sixth costume of Nijisanji's Gundou Mirei, as seen on Twitter.
It is a composite costume, with a shared base consisting of a black dress with floral patterns at the bottom, fishnet gloves, and an ascot held in place with a gem. Using various accessories, she can don one of three looks, the first being a maid appearance, the second being a military uniform, and the third being mourning clothes, with the ability to mix and match between the three's unique assets.
This tag implicates gundou_mirei (learn more).