Masamune, who died in a traffic accident, is granted a new life by a goddess and sets out on a journey to defeat the Demon Lord in another world.

Masamune, an otherwise physically ordinary boy, was granted only one cheat ability: 'magical cards with special effects'. While each card individually holds no significant power, Masamune was, in fact, the Japanese champion of a trading card game.

Using card combinations no one could ever predict, Masamune successively defeats the Demon Lord's army. As he gathers allies and steadily increases his hand of cards, he eventually comes to be known as 'The Sage of the Demonic Grimoire'.

This is a story chronicling the great feats of such a boy, Masamune, leading up to his defeat of the Demon Lord.

The 'book version' is now available from KADOKAWA BOOKS.

（※Title changed on December 24, 2015. Former title: 'The Sage of the Demonic Grimoire ~There Was a Time I Also Thought I Could Rise to Power with Card Abilities~'）