Butcher Demon - Chapter 7: Working Outside.

Zhong Li, an orphan in the 21st century, was wondering how to collect the fees for his college study on the street, when he was suddenly hit by a car, which threw him into a river. An orphan’s disappearance would not bring too much attention to the world, but this accident gave Zhong Li another chance of living a glorious life in an immortal world. When he woke up, he found himself lying in a magnificent yet strange palace built of all gold, but had no door. An immortal claimed to be his savior and wanted to train Zhong Li with all of his cultivation methods, only because he was too lonely and wanted a disciple to keep him company. When Zhong Li finished his study, the master would tell him how to go out of the palace. Zhong Li never thought that the path to immortality would bring him to the fate of becoming a dragon.

- Description from Novelupdates

My past life: Ordinary. Mediocre.

Following a brutal and tortured death, a former assassin, known only by his codename Kuro, is given the opportunity to reincarnate in another world, a world with magic and monsters. Armed with an unrivaled healing factor and an inhumane pain threshold, Kuro opts to go for a reckless direct approach in this world instead of a stealthy and cautious one, and as a result, slowly gains attention bit by bit.

Having previously been a loner in his old life, he interacts and befriends people for the first time in his existence, however, his blunt nature also sees him making just as many enemies, both big and small. By combining his old assassin skills with the magic powers of this world, along with his high resistance to pain and rapid regeneration, he doesn't take long to establish himself as a formidable force in this world.

Initially, Kuro only faces minor threats, like weaker monsters and bandits. But before too long, the threats slowly but surely become more and more severe…from Zombies to a bloodthirsty empire to Vampires and Demons, and even divine beings…however, as the enemies he faces grow stronger, so does Kuro, gaining rare powers that have never or rarely ever been seen in this world…

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