In the mid-21st century, Tokyo's underworld is ruled by mafias who have transformed into "Demon Lords"—monstrosities empowered through Ether-enhancemnt surgeries.

The bounty hunters who hunt these Demon Lords down... are known as "Braves."

Enhancing their own Ether abilities with a drug called "E3," these Braves fight back. With lethal force legally sanctioned, being a Brave has become a profession of licensed murder.

Enter Yashiro, a freelance Hero known as "the Grim Reaper." One day, a self-proclaimed "apprentice" barges into his life—Jogamine, a high school girl training to become a Brave.

Reluctantly taking her under his wing, Yashiro finds himself dragged into one chaotic mess after another!

A scumbag master and his self-proclaimed apprentice－the curtain rises on a blockbuster modern urban fantasy action!