Undead Unluck follows a young woman named Fuuko Izumo, who suffers from a curse called "Unluck"—anyone who touches her experiences an overwhelming string of misfortune that inevitably leads to their death. Fuuko is an outcast, burdened by the inability to control her curse, until she meets a mysterious, immortal man named Andy. Andy is cursed with "Undead," which means he cannot die, no matter how grievously he is injured. He seeks to end his life and believes Fuuko's curse may hold the key to doing so. Together, they embark on a dangerous journey to find a way to end his immortality.

As they travel, they encounter other individuals who possess strange, supernatural abilities known as "Negators." These abilities are linked to various forms of misfortune or luck, and Fuuko and Andy become entangled in a larger conflict involving the Negators and a shadowy organization with its own hidden motives. The manga blends action, dark humor, and emotional moments, exploring themes of fate, personal freedom, and the search for meaning in a chaotic world.