You Promised Me Darkness

Approximately every 75 years, Halley's Comet orbits around the sun, and every time this happens people around the world are born with incredible abilities, special auras that grant them with supernatural skills, but those auras can also be cursed. Yuko and Sebastian, two siblings with special auras are constantly running from an evil being, known as the 'Anti-everything,' who feeds from these special auras, getting stronger with each intake. This being is obsessed with these brothers' auras and will not stop until he feasts on them.