Kirigakure Gamer : Rise of the mist - Chapter 17: Fog Kenjutsu Dojo Master

A cauldron, a secret forging method, and his blood created an ultimate weapon. The youngest Sword Crafting Master on Earth had been reborn from another world. With the Nine Yang Divine Furnace and a scroll of Divine Equipment, he was like a fish in water, standing at the pinnacle of the martial way. There were tens of thousands of clans, billions of cities, and countless experts. He was the master of ups and downs!

I lived for you in the last lifetime, everything I did was for you, yet you wanted me to die; so, this time, life is mine to live! This world lied to me, betrayed me, and humiliated me, and I am back to change everything!

- Description from Novelupdates

In a future city intertwined with science, magic, and various races, a fearsome villain lives.“How dare you try to use such a young child. Do you have no conscience?”“It’s truly regrettable. To think that this girl could be the key to eradicating a den of evil.”“You can rest easy now. We will definitely protect you.”Sorry, but I’m actually that villain…It seems like a serious misunderstanding.

An orphaned boy with dreams of making it big through being a blacksmith is given a once in a lifetime chance to succeed when he's taken in by an odd pair - Eggor and Ella. While former teaches him the arts of craft, the latter teaches him the mysticism of cultivation, granting him two paths to tread in this life.