Fanart of Mimi. Source
Mimi is the protagonist of the game with the same name: Mimi.
Because the game is completely done in a monochrome scheme, Mimi's palette is limited to the colors black and white. Her skin is completely white as the center of her eyes, while her shoes and twintails are completely black.
She is wearing a black dress with a little white dot on the lowest point of her chest.
Not much is known about Mimi's personality but it seems that she has out-of-body experiences.