Zero (零 Zero) is the main character alongside Kurohime. He is known for quick drawing four guns at lightning fast speeds, earning him the nickname Zero of the Superfast Quadruple Guns. He has a strong sense of justice,believing that "the gun is the sword of justice," instilled in him when rescued by Kurohime as a child. This prevents him from killing; instead, he disarms or immobilizes the enemies.
Zero has a fairly skinny build and a "babyface." Parts of his semi-long, blue hair cover his face while a streak of black comes down between his eyebrows. He has light blue eyes. He wears a long blue scarf around his neck and an outfit of white. On both arms he wears blue wristbands with the same pattern as his scarf.
At a young age Zero was saved by Kurohime, a witch-gunslinger, from a bandit. It was that event that started his belief that "the gun is the sword of justice." He also realized he had fallen in love with Kurohime. Over the ten year period prior to the start of the series he trained to become the best gunslinger, developing the quickest quickdraw. He became famous as "Zero of the Quadruple Guns."
Gousokuryou Zero: A form that Zero takes after being hit by Kurohime's Mariikudan bullet, which turns him and gives him the power of a dragon. It also gives him high speed rapid firing.
Dark Zero: Zero's soul that is taken to the underworld by Yashahime and there he is resurrected as "Dark Zero" (堕悪“零” Dāku Zero?) the new God of Death. The two later confront Kurohime at the prison of the Spirit King Byako and attack her, even though she isn't willing to fight him. After taking back his signature blue scarf from Kurohime, he tears out most of the petals that comprise her soul lotus, leaving one behind. This single lotus petal contains the memories of the love Kurohime has for Zero, and the pain of losing him. This act causes Zero to remember his true memories and he transforms into his full Death God form. It is revealed that Zero holds much darkness in his heart, as the "Good Zero" is told to be just "an image created by an idealistic youth". Zero continues the fight but later retreats with Yashahime after she was severely injured by Kurohime. While Kurohime was gone into Zero's past, Dark Zero declared that he would wipe out humanity, and would ask the Supreme God, Igudo, to commence with the apocalypse.