The Grim Reaper is My Guardian

Ok-Ji Mun can’t escape bad luck. From tripping in class to near-miss accidents, her life has always been one streak of misfortune after another. What she doesn’t realize is that her best friend, Ha-Seong Ji, is actually a Grim Reaper assigned to keep her safe. When the truth comes out, Ok-Ji learns her fate has changed and she has only 30 days left to live. A strange method might let her alter destiny, but it comes at the expense of others. As high school drama collides with a mysterious threat, Ok-Ji must decide what to do before time runs out.

(Source: WEBTOON)

Note: Includes one extra chapter.