Chrysalis - Chapter 4: The first prey

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Jang Joonbum started stream to enjoy an easy life.

An AI calling itself Schema has assimilated earth into its system. As a consequence, everyone gained access to status screens, power-ups, and skills. This AI turned these concepts from fiction to fact. It's easy to become intoxicated with leveling up and becoming stronger. To some, it's too good to be true like living out a dream.

For Daniel, however, it's closer to a nightmare.

He's in a bit of a predicament. Cracks in our dimensional fabric have unleashed terrifying beasts from dark, abyssal places. Schema organizes these cracks into dungeons, giving the native species of the planet a chance to fight back. Daniel finds himself trapped in one of these dungeons. Not long after, he discovers there's only one way out.

After Xia Feng transmigrated, his heart was mysteriously removed.In its place, a defective demon heart capable of sustaining life only for eighteen years was implanted.This is a magical heart that can sync with the power level of its target.To stay alive, he bound himself to the ultimate villain of the future, a Destructive Witch who was destined to destroy the world.The stronger the Destructive Witch becomes, the stronger he becomes!Thus, Xia Feng realized, it's not my fault for stirring up trouble: “Miss Witch, I admit you're strong, but not strong enough!”