Kurumi is the first Steel Angel, and she is awakened when Nakahito kisses her. Nakahito is the second child of Onmyoudou Shuke (a house of a Japanese Yin and Yang spiritual leader). Kurumi has so much affection for him that she calls him "my master", and only follows his orders. Now, Nakahito, a boy with a gentle heart, and Kurumi, an android with an Angel Heart and incredible power, join forces. When the second Steel Angel Saki, the third Steel Angel Karinka appear, things really start to mix up...

The high school student and aspiring cellist Kagura Nako accidentally discovers and kisses Kurumi Mark II at her home, thus making herself Kurumi's master. Things go awry as Nako's best friend Uruka gets jealous and tries anything to destroy Kurumi and win back Nako. Things get more out of control when Saki Mark II is awakened by Uruka, and Karinka Mark II joins in to steal Nako away from Kurumi. [Set 75 years after the first series. A new chapter in the story of the three female androids.]