Yume Nikki:Monoko

Monoko Event BGM

Monoko (モノ子, "monochromatic girl") is a character in the White Desert A. She appears to be a black and white girl with cross-shaped eyes and an open mouth. Her name comes from the Picture/モノ子.xyz file in the game, and is thus one of the few characters with an official name other than Madotsuki, Monoe and some others.

She is found in one of the White Desert A's tunnels, and seems to move back and forth faster than most characters, perhaps a way to subliminally nudge the player to use different effects on her.

Her usual appearance only remains until you use the Stoplight on her. She immediately stops moving and changes into a different form: She now has five arms, one of which sprouts out of the top of her head; her stomach grows what seems to be a bloodless wound or vortex; and her left eye and mouth begin to melt or dribble, which is usually interpreted as her crying and drooling.

If you run into Monoko while she is in this form, a full-screen event shows a detailed picture of Monoko bouncing, spinning and zooming in and out on the screen to a beat similar to that of the KALIMBA event (BGM_022).

Trivia

Collectively by fans, she and Monoe are called the "Mono Sisters", alluding to the fan theories of them being sisters.
Another interpretation is that she is also related to the game's theme of traffic accidents. As her second appearance is triggered by the use of the Stoplight, it led to fans theorizing that her second form represents injuries related to a traffic accident.
In Japan, it is traditional to take your shoes off before committing suicide. Monoko is depicted without shoes, which could be a form of foreshadowing.