MTL - Half Immortal - Chapter 43 Ankang Ancient Town (No. 22)

High school student Mikoshiba Ryouma was summoned to a different world in the middle of a war. Sensing the malice from the one who summoned him (a summoner of the O’ltormea empire), he uses his martial arts to run away, killing important people of the empire during his escape. After the escape, he rescues two twin sisters from the hands of thieves. The sisters who can use magic, swear to serve him as subordinates. Thus, Ryouma begins his journey on the path of the supreme ruler.

The Earth of the future is united under a single government, but not all things are well. The shape of the playing field may be changed, but the powerful still rule the weak.And those who do not conform with the rest of society are exiled to another world. A world that not even the technology of the future managed to tame.It should have been humanity's New World but ended up as nothing more than a penal colony. A place where the exiled are sent to die.Motivated by revenge, Magnus sets out on a quest to bring his own justice to his enemies. For that purpose, he is willing to go further than most others.But then he learns that if he truly wishes to change things, he can only find his answers beyond the gate.Having lived most of her life as an exile, Astra is a woman of few interests aside from survival and climbing the ranks of her clan.To achieve those goals, she certainly won't be squeamish when a chance literally falls into her lap, or will she?———————————————————————————————I am trying to go with a survival/“no modern tech” setting in this one. People from a technologically advanced society are thrown into a world where they can't maintain their tech. They are forced to rely on what the world provides where they have to make do with the limited resources they have and what little of their old technology is still working. Their gene manipulation allows them to have something akin to superpowers, but that doesn't help much against the monsters of their new world. Not sure yet whether sufficiently advanced technology will be discovered later on to count as magic.It turns more political between the various clans later on.

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

5 years after the world changed, the final boss appeared.