Year 20XX, strange phenomena started to occur all around Japan. The best way to explain it would be a ''hole'' that connects different worlds to our world. Many otherworldly beings - magicians, demons, robots and other fantasy creatures started to appear on this side, with no way to return. With the time passing, Japan was able to adapt to this event and visitors from another world stopped to be anything unusual.
And so, an unlucky witch named Henrietta was pulled through the ''hole'' and ended in modern day Japan without a way to return. How will she be able to live in this different world?

A mecha otaku is reincarnated into another world as Ernesti Echevalier (Eru). In this world, exist huge humanoid weapon known as Silhouette Knight. Dreaming of piloting those robots, Eru, with childhood friends, Archid and Adeltrud Olter: together they will aim to become Knight Runner, pilot of Silhoutte Knight.