The third costume of hololive's Uruha Rushia.
It's a gothic lolita-themed black off-shoulder dress with short sleeves with criss-cross frilled straps and see-through sleeves, a black lace choker, black wristbands and white frilled thighhighs with white garter straps.
She has a variation of this costume (post #4323254) with pierced cat ears with an ear ribbon and ghost-shaped earrings, also for her second anniversary got another variation of this costume which changes her hairstyle and adds a tilted mini crown and a black coat with a popped collar, which she wears on her shoulders.
She has several official hairstyles with this outfit: