Prime Originator - Chapter 724 - The Demon King's Intention

This is a story about Gong Lixin who was the young master of an ancient underground palace in the ancient times. He was raised by his master and forced to partake sexual relationships with numerous people to cultivate his Yin Body. His master who has a Yang Body was going to absorb him after he has reach a level to become stronger. MC refused and killed his master also dying at the same time. Then he transmigrated to the modern time and thinking he will enjoy peaceful life, the end of the world arrived.

'Confucius spoke not of the bizarre, the valiant, the rebellious, nor of spirits and demons.'This is the story of Mok Gyeongwoon, AKA the First Heavenly Demon - Cheon Ma, the forefather of the main character of the popular novel and manwha Nano Machine. This story is the prequel to Nano Machine, taking place 800 years earlier.

He Lang died by his own hands for the sake of his imperial younger brother’s ambition, whom he loved. He was offered to be reborn in exchange for giving up his past romantic feelings. Reborn without the burden of his romantic feelings, he brings with him a manual to new worlds. He wholeheartedly followed the instructions of the manual to complete the tasks, not knowing that the originally slag gong was blackening…
He pleaded to his affectionate Emperor brother to release him, he pleaded to the paranoid prisoner next door, but until the end he remained baffled.
In the end, he discovered that the full name of the manual was – “Slag Shou Cultivating Manual”
Σ (っ ° ° °;) っ!

- Description from Novelupdates

In a world where life energy fuels martial prowess, Shen Yifan, with a mere mortal lifespan of a hundred years, finds solace in slaying demons to extend his own vitality. Amidst the chaos of a realm teeming with malevolence, he brandishes his blade, striking terror into the hearts of creatures who have roamed the earth for centuries! Yet, amidst his valiant exploits, Shen Yifan sometimes ponders, why does his lifespan seem to dwindle faster with each use of his powers? Sheathing his sword, he gazes skyward, hearing tales of the divine palace in the heavens, where immortal beings dwell, having weathered endless eons. Embarking on a celestial journey, he seeks to beseech the gods for a loan of a million years, to pave his path towards eternal life.