||Death Grave Keeper
is a mysterious blond boy who is an acquaintance of Shuichiro. During Shuichiro's coup d'état and the second Apocalypse outbreak, Yuu is revealed to also possess the Power of Kings when he kidnaps Inori and uses her void to kill Shu only for Gai to save him. Gai recognizes him by the title "Grave Keeper of Da'at". It is implied that Yuu comes from the Daath Society, which is an ancient secret organization and possibly, the main antagonist group.