The Sword and The Shadow - Chapter 31 – Harves

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

A world where God will grant abilities called Skills to those who come of age. The protagonist, bestowed with two skills, uses them and rises to an existence called a hero.

While reading a book, a sparkle of light disappeared. And, as it did, a message appeared.