I Became a Scumbag in The End Times With a System and a Wife? (GL) - Chapter 8: Crystal Cores! - Killing Zombies!!

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

Forget about moving to the other side of the world and starting over.The Apocalypse is here!As the only survivor of the Tutorial Quest in his area, Elijah awakens the Class of “Depraved Hero”, an ominous-sounding Class with a Legendary Rank!Additionally, because of the insane difficulty as well as his Clear Rank, he gains the Skills that, according to the mysterious figure that is the Administrator, he needs most.[You have Developed the Skill “Absolute Authority[A]”.][You have Developed the Skill “Slave Mark[C]”.]

In this brutal world ruled by the law of the jungle, Ximen Wei is driven by his desire to return home and escape his past regrets and feuds.

As he becomes increasingly obsessed with achieving his goal, he loses his emotions and humanity, resorting to any means necessary, no matter how unscrupulous or immoral.

He becomes a symbol of massacre and death, a demon god feared throughout the Qi World for his willingness to kill anyone who stands in his way or possesses something he needs.

Follow Ximen Wei's journey as he rises to power, terrorizing those around him in his quest to become a powerful demon god.

After a tear in reality pulls Kagari Shuya into a white room he discovers a futuristic interface for reincarnating in a different world. After looking through the different races and skills he unlocks a new race, Lucivault, a type of vampire with none of its characteristic weaknesses. All set to start his life in a new world, Shuya is confused to discover that he is enveloped in darkness. As it turns out something went wrong when he was transported and instead of appearing where he was supposed to, he appeared in an underground cave. Shuya faces untold dangers, runs for his life, before finding his way out of the underground world. After escaping he meets his Shishou and begins to learn to fight with a spear. There is also a cute black cat named Rollo.