Twelve Demonheart Series

Twelve Demonheart Series (12-デーモンハートシリーズ) is the term given to twelve bioweapons which were created for saving humanity from Akuma.

History
A long time ago in the so-holy city "Tokyo", numerous holes opened across the world. From that hole, demons called Akuma started emerging and began attacking humans. Humans tried to respond with war but no weapons or machines could stop them.

To take action, leaders of every nation decided to make an Anti-Demon Squad. This squad was called the Twelve Demonheart Series and were made using the Demon's own power. They were living bioweapons and have the absolute directive to protect humanity. Each unit of the series wields power based on a certain development concept, resulting in a very different expertise for each one.

As years passed, all of them continued to age and eventually die except Leo Demonheart.

Leo Demonheart
Unit DH-05 Leo, the protagonist of the story based on the concept of infinite evolution. The only surviving unit of the Demonheart series.