A blonde-haired, gold-eyed witch wearing a hooded sleeveless jumpsuit with a black color scheme. Her symbolic animal is the snake. Her personality is pure evil. She literally stops at nothing to achieve her goals, possessing a cold-blooded ruthlessness that disposes of enemies without hesitation. Furthermore, her acting skills are so superb that she hides her true nature and lies without a second thought. However, because she possesses a terrifying level of meticulousness and confidence, she leaves a much stronger impression than a simple villain. She usually has a sharp, beautiful appearance, but when her true nature is revealed, her expression becomes eerie and demonic, reminiscent of a snake. Her catchphrase is telling her opponent that they need to be punished. Not only did she transplant Black Blood and Ragnarok into her own child, Crona, but she also raised them through abuse and neglect from a young age to turn them into a Kishin. As a result, Crona's emotions have become almost entirely withered, bordering on emptiness except for madness. The existence of her husband is unknown. Given her personality, she likely used him as a tool and then discarded or killed him. Her specialty is Vector Arrow, which creates arrows on the ground to launch targets in the direction of the arrows. Her other abilities include summoning snakes.

Gender is male. He has purple hair and black eyes. He grew up with a timid, dark, and unstable personality. However, when entering battle, he shifts into a more aggressive persona. He resists the bullying of his partner and Demon Sword, Ragnarok, but it seems that if he were to fully surrender, his soul would be completely swallowed by madness. His catchphrase is, "I don't know how to deal with this." Unlike the typical relationship between a Meister and a Weapon, the Demon Sword Ragnarok is melted into Crona's blood and flows in liquid form. In other words, the Meister and the Weapon share a single body. Because of this, he receives more active support than any other weapon; the Demon Sword Ragnarok supplements the physical strength of Crona's thin body and even makes tactical combat decisions. Furthermore, by controlling the Black Blood mentioned later, Ragnarok directly assists in combat, providing many advantages compared to other Meister-Weapon relationships. He possesses Black Blood in his body. Since this Black Blood has the property of hardening and can be controlled by the user's will, most physical attacks do not work on Crona. Even if his skin is cut, the attack is blocked by the blood vessels where the Black Blood flows, and even if his body is cut, he can stop the bleeding by hardening the Black Blood. Uniquely, he uses Scream Resonance rather than Soul Resonance. Originally a soft-hearted and timid child, he became completely passive after receiving "education" (which was actually abuse) from his mother, Medusa, since childhood. Consequently, he appears to be very afraid of Medusa. He does not call her "Mother," but addresses her as "Lady Medusa." The incident where he was forced to kill a small rabbit as a child—repeatedly failing to do so and being locked in a dark room until he finally killed it—remains a deep scar in Crona's heart to this day.

The owner of a violent personality who constantly bullies his partner, Crona (often hitting him on the head or distorting his face). He is a weapon of a peculiar form; he appears as a black, bizarrely shaped humanoid with only his upper body emerging from Crona's back, rather than looking like a normal human. As a weapon made of Black Blood, he usually stays inside Crona's body, mixed with his blood in liquid form. After transforming, he becomes a longsword with a black blade. A mouth appears on the blade, which he uses to scream and vibrate the sword, creating shockwaves or delivering additional attacks. He likes sweets.