The Return Of the Invincible Heiress - Chapter 300

Everyone has a system they just need to meet hidden conditions to unlock it. A blacksmith system may unlock after a human walks by a forge. A master mage may unlock a system after attempting to control the mana in their body. Even something as simple as kicking a rock at a bucket can unlock the marksman system a unique system allowing for perfect accuracy. But what happens when someone reaches the age of fifteen and hasn’t unlocked their system? Walker is about to find out, time is ticking and he doesn’t want to live out his life as an ordinary human; he has dreams you know!

Damian, a Centurion of the Punishment Unit of the Baroque Kingdom. “Damn it.” Just once. If I were given just one more chance… ‘I would have truly conquered the battlefield with these guys.’ At the age of 30, he closed his eyes on a nameless battlefield. But when he opened them, he found himself back 17 years in the past. And this time, he had a perfectly functioning mana core that could wield magic. ‘This time.’ I will rise higher than anyone else. I won’t be swept away by the turbulent times. ‘I will conquer.’ Damian, who has returned to the past, wields his spear toward the world.

Liu Duo was a young girl whose grandmother sold her to four brothers with the intent to be a bride. Unwilling, she ran away the following night, only to fall unconscious while trying to get away. Unexpectedly, however, she was reborn with the spirit of a 25 year old woman, also named Liu Duo.

- Description from Novelupdates

After the nuclear warfare, massacres started to spread throughout the entire world. The order between humans completely collapses, and the strong eats while the weak gets eaten becomes the #1 rule.