Rikka, the oldest daughter of a Ninja clan, resides in a covert ninja home situated in a futuristic metropolis. She admires her father, a well-known researcher, greatly. While leading a routine life, Rikka's abode is unexpectedly ambushed. Cornered and under pressure, she must come up with a plan to combat this dire situation. In response, she will vanquish the looming darkness and transform into "BLACK".