The Strongest Gene - Chapter 12: Unexpected Mutation!

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

A thousand years ago, the Great Calamity struck Earth. Countless rifts tore through reality, opening portals between the Demon Realm and the Human World. Overrun by monsters, humanity was on the brink of extinction. But at its darkest hour, something miraculous happened—those who died returned, awakening strange new powers that allowed them to fight back.Vale knew that story well. Maybe that's why he wasn't surprised when he heard the voice of the system speak to him.[ Congratulations! You have died. ][ Your First Trial of Death begins now. ]What truly shocked him, however, was the question burning in his mind:“Who would dare to assassinate the Second Prince of Verythmia?”

Bro, I mean, I'm just a tad handsome, a bit skillful, and slightly crafty, that's all! Why do you all have to make my life difficult? This incessant pestering isn't the answer, is it?What? You'll marry no one else but me? No...you...how could you? Without even asking for my consent?

Greed, envy, anger, gluttony, lust, sloth, prideThe 'Black Book' records seven sources of sin, which are also seven steps to ascend to godhoodOnce, I thought there would always be one sin suitable for meBut I never expectedEvery volume of the twelve military letters bears my name!