Toaru Majutsu no Index: Genesis Testament - Volume 4, Chapter 4: Beyond the Two Choices – Duel_Against_R∴C∴O∴(for_Save_Mother).

When Arran decides to become a mage, he quickly discovers that magic can be more dangerous than he had ever imagined. Soon, he finds himself hunted for powers he never knew he had.

«Grey, elemental affinity, zero» The Elder announced the result loudly.

Son of a bitch! I just finished this godawful fantasy novel, and now I'm knee-deep in it – as David, the disgraced son of the Solarian Empire's top general! Talk about some twisted cosmic joke. But hold on a damn minute... maybe this isn't all bad. Armed with the knowledge of that trashy plot, I can become the ultimate shadow player, an overlord perhaps. Screw the damsel-in-distress harem too – it's time to pull the strings and become the real power behind the throne. This isekai might be a steaming pile, but I'm rewriting the ending with a little more... Debauchery (wink wink).

Cifer was offered as a sacrifice to the devil by his own family. Instead of dying, was given a chance to live in another world. The One True God has given him a mission. Stop the higher being calling themselves gods from snatching soul from the life stream and restore balance.An adventure will begin from a devil's sacrifice to be one of the most powerful beings seen.With a body of a titan and souls of devils, grasp power and devour everything for happiness and freedom.