Isekai Maou to Shoukan Shoujo Dorei Majutsu - Volume 7 Chapter 4 part7

After falling to my death, I woke up with two bodies?!Reincarnated as both a humble commoner boy and a privileged young noble girl, our protagonist enjoys their new chance in life with two different perspectives. Although they only wished for a peaceful life, the world had other plans in store, presenting them with a few unexpected obstacles along the way.Now, they find themselves confronted with bandits, secret evil organizations, terrifying monsters, and... romance?

Thousands of years ago, a small planet collided with Earth and destroyed the world. In five days, ninety percent of humans had been wiped out, leaving behind the last ten percent to earnestly struggle on death’s door.

Jinyu was one of those people who survived. Due to a special heredity trait, he could understand beast language. After the apocalyptic disasters, Jinyu had been living for a month with the few small beast brothers that he’d subdued. Previously, Jinyu had thought that he would live like that until he died. Yet, inexplicably, one day he opened his eyes to find that he was in a monstrous, lawless world that was full of vitality and life.

Jinyu’s transmigration into the future let him skip over almost one hundred thousand years. In the year 106825, beasts rule the galaxies and ‘pure’ humans are extinct. As the one and only ‘pure’ human left in the entire universe, Jinyu braves this new chaotic world to find a place for himself and thus begins to work at Beast Store number 138.

- Description from Novelupdates

Yeon-woo had a twin brother who disappeared five years ago. One day, a pocket watch left by his brother returned to his possession. Inside, he found a hidden diary in which was recorded “By the time you hear this, I guess I will be already dead….”

Shaymon, the man who has achieved the apex of dark magic, is framed as being a Demon King and is killed.