This story was very tragic. It told us about "Fallen Imugi".
In the Korean folklore, when Imugi ascend to Heavenly Realm to become a full-fledged Dragon, they must not be seen by human(mortal), or else their ascension will fail and the Imugi shall fall back to Earth.
MC was a Brown Sparrow that was saved by the Green Imugi in the past, who somehow got reincarnated and possessed "Fallen Green Imugi" Yeouiju in the present times. His role is to absorbs "Corruptions/Misfortunes/Curses" that befell the Green Imugi.
The Scarred White-Haired man is a White Imugi.
Black-Haired Man is a "Fallen Green Imugi", who got cursed after failing to ascend and lost his Yeouiju.
The plot is very similar to KDrama "The Haunted Palace".
This is a quick and not detail summary but pretty much the black haired guy is struggling with his powers or something, and he’s honestly kind of an asshole. He never really improves, and you shouldn’t expect him to. He treats the MC terribly, and the only time he shows any kindness is when he talks about his tragic past which only makes the MC pity him. And the black hair is always sick which again make the mc pity him.
The white-haired ML is much kinder. He worries about the MC because the black-haired guy literally abuses him. But the MC only sees the white-haired guy as a friend… or someone he can lean on when he needs help. In the past, the white-haired guy was actually murdered by the black-haired guy because he couldn’t control his powers.
In the newest chapter, the black-haired guy kills the MC, and the white-haired guy is trying to save him. The MC is probably dead because the black-haired guy choke him. That's what the story is.

Bruh I just read the raw and reading it made my head hurt like who tf wrote this