The Uryen are weapons that came to our planet when Datatsushi landed. Their origin, purpose and creator is unknown, though it could be related to Datatsushi, possibly created by him, or at least items he had with him in his ship. The Uryen can permanently kill a Shibito or a Yamibito by unleashing blue flames upon them. There are two methods of releasing the fire, as demonstrated by Kyoya Suda; one is by concentrating a massive flame into one spot, and the other is by sending down fireballs to devastate enemies across a wide range.
In 1976, both Uryen statuettes were held onto by Miyako Kajiro (1976), and due to her incapability to move due to Hisako restricting her, the Uryen were trapped with her. In 2003, Shiro Miyata discovers Miyako and obtains Uryen from her.
As a weapon, the Uryen requires the life-force of its user. Since Kyoya Suda is immortal, resulting from his cursed blood, he is able use the Uryen an unlimited amount of times. With Shiro Miyata, the use of the Sword Uryen upon granting his wish burns the arm he used to wield it.