On everyones birthday at noon, one word appears on their skin, depicting their career or purpose in life. On your birthday, youre staring at the clock showing Family and friends are gathered around for your reveal.
Others have commented the assassin is a time traveller. Time travel has nothing to do with it! Affect an unrelated thing in such a way that the knock on effect leads to the death of the intended victim.
And a girl/boy, everyone s/he cares about is raised from the dead, but when you are, you can’t see the dead (Vampire Diaries, the other side- kinda thing). Anyway, s/he does everything to come back to life, but Death/Life (person) will not let him/her. And everyone ends up leaving him/her, and forget