During Japan's Taisho Era (1912-1926), a scientist named Ayanokoji developed the Steel Angel - an artificial humanoid with superhuman physical abilities. While the Imperial Army wanted to use the Steel Angel as a new means of modern warfare, Ayanokoji wanted his creation to be a new step in the future of mankind. Thus, he defied orders from the Army and secretly made the Steel Angel codenamed "Kurumi". Then one day, a young boy named Nakahito Kagura snuck into Ayanokoji's house as a dare by his friends and stumbled upon Kurumi's lifeless body. A sudden attack by the Imperial Army shook the house, causing Kurumi to fall on Nakahito. At that moment, their lips met, and Kurumi woke up from "the kiss that started a miracle".
Now that Steel Angel Saki Mark II has been activated, Uruka tries to make her fight against Kurumi.
Saki tries to get Kurumi and Uruka to be with her, but ends up being used as bait set up by the newly-activated Karinka Mark II.
Kurumi finds herself fighting the powerful Steel Angel Karinka.
Kurumi and Karinka get in an argument and accidently break Nako's cello. So, while Nako practices her cello skills with many other cellos at Uruka's house, Kurumi and Karinka get part-time jobs to buy a new cello for Nako.
Nako's cello contest is coming soon, and if Nako wins, then she will get to study abroad in Vienna. Kurumi and Karinka contemplate on how to feel about Nako going away. Meanwhile, Uruka persuades her father to use a special suit to prevent Nako from leaving her.
Can Kurumi keep Karinka and the battle-suit-equipped Uruka at bay and make it to the cello contest before Nako's turn comes up?
Karinka's new goal is to get a kiss from Nakahito so that she can become more powerful than Kurumi.
A couple of incidents get Kurumi thinking that there is something going on between Nakahito and Saki.
Nakahito makes one final attempt to stop Kurumi from destroying everything.
Nako Kagura is a girl skilled in playing the cello. One day, she and her friend Iruka go down an underground cavern, which has a statue containing Steel Angel Kurumi Mark II!
Uruka's dad discovers a Steel Angel like Kurumi named Saki. Uruka snoops around Nako's house to find the manual on how to activate Steel Angels.
The battle between Kurumi and Mikhail continues. However, Kurumi is being consumed by demonic energy to the point that she grows black wings.
After Kurumi (in demon possesion) attacks the academy base, the damage is fatal. So 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.
After beating Mikhail, the demonically possesed Kurumi attacks dr.Walski's base!
Karinka finds herself working as a waitress with Kurumi and Nakahito in an effort to find out the secret to Kurumi's power.
Kurumi is released from her capsule and kisses her new master who just happens to be a girl... the girl's mother welcomes Kurumi with open arms and helps her get an outfit for Kurumi shall be joining her new master at school, which someone close to Nako isn't happy about.