The Overlord of Blood and Iron (WN) - Chapter 14

I really just want to lose money! T_T

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

High school student Misumi Makoto is called into a fantasy world by the god Tsukuyomi, in order to be a hero. However, the Goddess ruling the world isn’t as thrilled to have him there, and kicks him to the edge of the world. Tsukuyomi declares that Makoto is free to find his own way after Makoto is abandoned by the other Goddess.