Immortal Days

Mankind has discovered the secret to immortality. As humans can no longer die, violence abounds. Living among the immortals is Myeol. Careful and conscientious, he’s a street-smart fighter who’s trained himself to survive. Why? Because he’s mortal; a mutant. Upon meeting Phill, a money-grubbing “Troubleshooter” short on morals, Myeol is thrown into a life full of guns, bombs and death cults. But Myeol and Phill have more in common than meets the eye...
(Source: MangaUpdates)
~~ Adapted from the webtoon "Immortal Days" (불멸의 날들) written by "Heo Gin Gae" (허긴개).