The Demon King, Saintess of Love in the next life?

Vorak is the Demon King — the most feared existence in the world, a conqueror who has never known defeat. But when a human woman walks into his life and a daughter is born with his eyes and her smile, he discovers something no army ever taught him: that the cruelty of his kind was never destiny. It was a choice. And choices can be undone. He spends the rest of his life proving it. But death, it turns out, is not the end of his story. A goddess has been watching — and she has decided that a soul which found love at the end of a long road of ruin is worth far more than one that never had to look for it at all.