Kyoukai Senjou no Horizon – Kimitoasamade - Volume 1A, Prologue: The Three Girls of the Asama Shrine

Junno is thrown into a fantasy world with starter equipment, a sword, and a bag of assorted coins. He decides to become an adventurer and earn money. Upon receiving his status plate, it appears that he has the divine blessing of many gods. Then he chances upon a s*ave.

"Your bed is cold," spoke a voice in the room that had her eyes go wide in fear. Nervously, she turned around, gulping softly to see a shadow on her bed as if someone laid down there. The man who had been lying down sat up emerging out from the shadows where he had been waiting for her.

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

This is a world where humans, demons and mysterious beasts coexist.

Humans cultivate mysterious qi. Demons cultivate corporeal bodies. Mysterious beasts cultivate soul perception.

A legend says that in the middle of an endless rainforest, there are extremely powerful existences; they are called demon kings.

Some demon kings have a tyrannical corporeal body, some are experts in illusions.
Some demon kings are proficient in magic, some can even move mountains.
Some demon kings are able to sense things thousands of miles away.

These demon kings rarely appear in the human world. Even if they emerge in the human world, they would reincarnate in human form; assimilating with mankind while seeking to breakthrough realms…

- Description from Novelupdates