Starting With Chaos Physique - Chapter 15 - Tuoba Siyus Request, Demonic Transformation

I was proposed to by the Final Boss.

The price for saving the world is the right to rule it. After saving a faraway land, Lyn Rivers was cast back to Earth. Wanting the admiration, prestige, and glory of saving that realm, she forced her way back. But she was forgotten, and someone else claimed credit for her deeds. Now, with the power of a deity of destruction, she desires nothing more than to claim her place in history. To do that she will conquer dungeons, make alliances, destroy kingdoms, and build an empire. After all, why ruin the world when you can bend it to your will?

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…

This is a story of a man named Kim Sae-Jin, who one day, inexplicably wakes up as a Monster. Follow him and his perilous journey to get his life back as a Human, all the while growing even more versatile as a Monster in the process. This should be… complicated, somewhat.