Mutagen - Chapter 1148: Violent Storms, The Night Goddess Pushed to a Corner

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

From the outside, Nana’s life seemed simple. She had everything she had ever wanted: a cute but rascally pair of twin brothers, a best friend, and her own restaurant. Nana couldn’t ask for anything more; she was happy and content in her life.