Seven Saga: Nanatsu no Taizai - Akakiryu wa Fundo ni Moete

is the first volume of the Seven Saga light novel series, written by Izumi Nishiki and Illustrated by Majiro and Eiji Abiko. It was released under the Dengeki Bunko Imprint in January 2016.

Synopsis
The time when God died. Draws a turbulent adventure of a man who contracts with the devil to protect his loved one. "Ruin due to betrayal" "Bounty hunter with children" "Repeated revenge" "Mighty and stupid king" "Endless interstate war" "Beautiful Paladin" "Legendary dragon" "The Seven Deadly Sins Mystery" An era when God dies and despair rules the world. There was a man who contracted with the devil for his loved one. He travels the world, goes through hell, and experiences a turbulent life, and eventually saves the world. This is the royal road! A thrilling, epic adventure fantasy !!

(source: Dengeki Bunko Official Website)