Durante a era Taisho (1912-1926), o governo Japonês criou o Steel Angel - um humanóide artificial com habilidades físicas sobre-humanas e grande potencial. Qualquer um desses androides possui habilidade suficiente para destruir um exército inteiro e se mantém inteiramente fiel àquele que o ativar primeiro. Um projeto chamado "Angel Heart Revised" foi criado pelo Dr. Ayanokoji, um homem que quer ver o bem da humanidade. O plano que ele traçou era criar o último Steel Angel melhor do que os outros, uma mulher chamada "Kurumi", e usar essa androide com a intenção de salvar o mundo daqueles que usariam o poder das Steel Angels para o mal. No entanto, as coisas não acontecem como o doutor planeja.
Nakahito Kagura and a few friends of his decide to investigate an abandoned house.
Since Nakahito's family has a history of magic, they decide that Nakahito should go with them to take care of the rumoured mad-scientist living there.
Dr. Amagi attempts to coerce Dr. Ayanokoji into working with the Japanese military.
Meanwhile, Amagi mistakenly grabs Nakahito and Kurumi has to rescue him.
A new character by the name of Dr. Brandow joins the Imperial Army, even more interesting is it seems as though he has been previously part of the Steel Angel Project.
Meanwhile, Nakahito must now become accustom to rude awakenings, while Dr. Ayanokoji is convinced the Imperial Army will not be able to awaken the second Steel Angel prototype.
The Imperial Army's preparation for the second Steel Angel's completion draws closer.
Meanwhile, Nakahito finds himself haunted by the words of Dr.Ayanakoji stating that only Nakahito has control over Kurumi.
As Kurumi finds herself forced into battle with Saki, she hesitates, giving Saki the upper hand.
In an effort to help, Nakahito seems to just make things worse and discovers that his words put Kurumi in this dilemma. As the fight continues it seems as though no one can help against the wrath of Saki.
What will be the final outcome?
With the kidnapping of Dr. Ayanokoji it seems that in return a new (and unexpected) member has joined in his place.
Meanwhile, Saki quickly redeems herself as she helps to rebuild what she had at one point destroyed.
The group"s trip to Izumo comes to a halt when Nakahito gets a stomachache.
Meanwhile, Kurumi, Nakahito, and Amagi go see a doctor, but this doctor isn't your normal kind of doctor.
A large boulder is blocking the path of the train to our comrade’s destination, Dr. Amagi searches for other transportation while the army tries to remove the boulder.
Meanwhile, Nakahito learns more about Dr. Ayanakoji's past from Dr. Amagi.
Kurumi, Saki, Karinka, and Dr. Amagi arrive at the Academy Base to rescue Nakahito. However, the Steel Angels fall into the Academy's traps, and Dr. Amagi meets face-to-face with Dr. Walski.
Kurumi (in demon possesion) attacks the academy base, the damage is fatal.
In order to stop Kurumi, all the steel angels drain themselves to the point of de-activation to power the ultimate weapon to stop Kurumi's destructive powers.