Technology has advanced due to the discovery of an alternative source of fuel called "Thunder-Cores." This has changed civilization for the better due to the creation of longer lasting trains and cars, and a new form of transportation called Air-Ships!

The story follows Tatsu Frampt, a young boy who lives in an orphanage nowhere near the city, who dreams that one day he will be the captain of his own air-ship and travel around the world alongside his friends. He is told that he and his friends are being isolated from civilization due to a disease that makes iron grow in their bodies. However, the orphanage is attacked, and Tatsu is the sole survivor, and learns the dark truth of his "disease." Six years later, he embarks on a mission to save his friends, and kill those who stand in his way...

(Source: MAL)

There's nothing. There's no one. There's a boy...

Teppei was just a normal, good-hearted kid who loved and idolized his father, a policeman, and aspired to become like him. He had friends at school, even a girl he liked. However, all this was thrown away on the day the world changed forever.

On that day, several people, mostly criminals and scum, inexpicably transformed in monsters; demons, and proceeded to lay waste to human civilization. Entire towns were razed to the ground, incountable innocent lives lost. Unable to find his father or his friends, Teppei almost falls do desperation when he discovers that he's also one of the newly-awakened demons. But in his darkest hour, the sight of his friends' plight of hope make him remember who he is, and what he strives for.

Teppei will not become a monster, nor a demon. He won't prey on the weak. He will instead prey on the other monsters, and protect the weak and innocent from them. He will become a knight that will protect everyone!

Included one-shot;
Volume 1: Iron Curtain