Yarinaoshi Majutsu Kikoushi no Saisenroku

is a Japanese light novel series written by Ikkei Jukkaidou, with illustrations by Rangetsu. The series began publication on October 10, 2015 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
Redo your destiny.

A rewrite fantasy that updates the history of defeat to victory!

Still, humanity was defeated.

Humanity's natural enemy "Leviathan" suddenly appeared in a world where "magic" and "mechanism" are compatible. In the face of an unprecedented threat, "magicians" and "mechanics" joined hands for the first time, and civilization accelerated at a stretch-still. History was one step further, decisively slow.

So we start over.

From the red sea of ​​despair where everything has perished, to the past.

Going back and going back-towards "that day" with the "magical enchanter (dehide)" that is the crystal of technology. Run through this world again and reach out again to everything that was once out of reach. Rewrite history and fate.