Köinzell is the main protagonist of the series. Originally named Ascheriit, he was a young swordsman who earned the prestigious title of Blatt Meister, or Blade Master, for his exceptional skill with a sword. He was one of fourteen elite warriors chosen by the Emperor to defeat the enemy nation of Wischtech. Ascheriit was among the four who successfully completed the mission, but upon returning, they were ambushed by seven of their companions who had abandoned the quest. These seven killed three of the four and framed them as traitors, claiming the title of the Seven Heroes. Ascheriit was brutally murdered by his former best friend Glenn, who gouged out his left eye and left his body heavily mutilated. He survived by feeding on a fairy, which regenerated his body but mixed his blood with that of the faeries. This transformation permanently altered his appearance, giving him pale hair and skin, red eyes, and a childlike, feminine look. He adopted the name Köinzell and returned twenty years later to exact revenge on the Seven Heroes, who have become powerful nobles and warlords hailed as saviors by the people.

Köinzell is driven by a deep desire for vengeance against those who betrayed him and a determination to clear the names of his fallen comrades. His personality is typically cold, brutal, and ruthless when pursuing his targets, but he is also capable of great care and self-sacrifice for others. Despite his revenge-fueled motivations, the heroic nature he possessed before the betrayal remains. He is regarded as one of the best fighters in the series, mastering the legendary Black Wing sword technique and able to create massive black chain-swords from his right wrist. He is empowered by the twin moons of the world, and if he becomes too fatigued, he shrinks into a small childlike fairy form until he recovers. Throughout the story, his role is that of a lone avenger who gradually forms bonds with new allies and begins to reconcile his vengeful mission with the remnants of his original heroic self. Key relationships include his former comrades, especially the traitorous Glenn, and the allies he gathers along his journey who come to believe in his cause. Köinzell undergoes significant development, starting as a bitter figure focused solely on retribution and slowly rediscovering his capacity for compassion and protection of the innocent.