MTL - Therapy Planet No. 13 - v2 Chapter 181 turn around

The Spirit Network, known as【Deep Sea】 connected five continents as human civilization surged forward; yet, they were oblivious to the impending eternal night. With the Extraordinary Awakening, the edifice was about to collapse. Flesh is weak and pitiful, how could one ascend? The story began when Gu Shen, an ordinary youth, received a ruler that bore the truth. He peeled back the corner of this extraordinary world, becoming the largest moth among the thousands that dashed into the flames. If winter is coming, I will climb against the steps, overturn the thrones of kings, shatter the crowns of falsehood, destroy the scepters of injustice. I will become humanity's last, Bright Barrier.

A con-man and policewoman that are legends of their respective professions suddenly die, then are reincarnated and return to the Tang Dynasty of ancient China as little kids.

Accepting their second chance and forced restart, they choose to use the modern knowledge and specific talents that they have in their previous lives in order to live comfortably in this new life.

- Description from Novelupdates

Hou Niao, devoted to seeking the Dao, found himself mistakenly sent as an undercover agent to the Demon Sword Sect, eagerly anticipating the day he’d be rewarded for his service and could return to the Daoist Sect… Only when he had become a towering figure in the Sword Dao did he sorrowfully realize that there was no one left with the power to recall him!

I finally managed to kill the demon lord.