Past Life Returner - Side Story 40. A Month Later - Kwon Seong-Il

In the foreign world, the martial artists dominate the world and the sword of the emperor controls the fate of hundreds of millions of lives! Long Yu, the number one killer on Earth, after dying, takes rebirth in this new world in an aristocratic family of martial artists but faces rejection because he is unable to practice martial arts.

- Description from Novelupdates

To Producers, the two of them couldn’t be more drastically different voice actors.

Transmigrated-into-another-world-three-good-citizen Gu Xizhou, in order to survive, became a demonic cultivator. No matter how bad or evil, he adapted.

But then…but then he transmigrated back.

The returned Gu Xizhou was very angry. The student that offered his body in order to resurrect him had used a formation that was purposed for summoning evil spirits. He, Gu Xizhou, prior to transmigration was a law-abiding citizen that upheld core socialist values, a three good citizen representative. So how come after transmigrating and coming back, he had become a heinous malicious spirit?!

In each and every one of the spirit worlds, the ghosts and spirits originally lived a Heaven is first and I am second kind of happy lifestyle, that is until in the unlimited spirit mission worlds, inexplicably and out of nowhere came a demonic cultivator.

The ghost and spirits: QAQ

- Description from Novelupdates

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.