Andy, a Negator with the ability "Undead", has been long in search for someone with the ability to give him a 'real deathʼ. Fuko Izumo has been distancing herself from others in fear of bringing misfortune to those around her due to her ability "Unluck". As Fuko plans on ending it all, a chance encounter with Andy makes her start seeing things in a new light. The two decide to join the Union, an organization which aims to control and protect the world from unidentified phenomena. With their newfound allies and armed with their abilities, Fuko and Andy take on challenging "Quests". Amidst clashing beliefs and faced against powerful foes, the two uncover the mystery of the world as they search for the "greatest death ever".