近未来の大都市の一角に佇む忍者屋敷。
そこで暮らす忍者一族である石動家の長女・律花は研究者である父親に憧れていた。
平凡で幸せな生活が続くと思っていたとある日、突然何者かによって屋敷が襲撃を受けてしまう。絶体絶命の危機に果敢に立ち向かう律花だが――。
闇を斬り裂く“黒”になれ！

Living in a ninja residence tucked away in a corner of a futuristic city is Rikka, the eldest daughter of a Ninja clan, who looks up to her father—a researcher—very much.
Carrying on with her life normally, Rikka's home came suddenly under attack one day. Driven into a corner, what would she do to overcome this crisis?
Rip darkness to pieces and become "BLACK"!