Jio Inzagi is an antagonist from the anime Blade Dance of the Elementalers. He is an orphan who was taken in and trained as an assassin by the Instructional School, the same organization that trained the protagonist, Kamito Kazehaya. However, unlike Kamito, Jio does not possess the natural ability to communicate with spirits, and his overall abilities were considered far inferior. To compensate for this lack, Jio was given a Cursed Armament Seal, a special mark on his body that allows him to seal multiple spirits within himself. It is said that he possessed as many as seventy-two spirits sealed within him, which he could command using a blood stone.

Jio has a distinct appearance, with dark brown skin covered in the tattoos of the Cursed Armament Seals. He has steel-like, spiky black hair and shiny red eyes, though his anime design gives him reddish hair. His personality is defined by a haughty and arrogant nature, and he harbors an intense jealousy toward Kamito. This jealousy fuels a deep-seated delusion, leading Jio to firmly and publicly claim the title of the Demon King, the powerful elementalist who serves as a dark legend in the world. He becomes easily angered when others dismiss his claim or point out that he is not the true heir to that title.

In the story, Jio acts as a significant early adversary for Kamito and his companions. His first major mission involves infiltrating the Areishia Spirit Academy to steal secret information about a sealed, war-class military spirit named Jormungandr. During this infiltration, he single-handedly wipes out a team of the Sylphid Knights and battles Ellis Fahrengart before Kamito arrives. His primary motivation is to prove himself as the true successor to the Demon King, which he believes entitles him to immense power and makes Kamito a rival to be eliminated.

Jios role brings him into direct conflict with the main cast, including Claire Rouge, Fianna Ray Ordesia, and the other members of Team Scarlet. His key relationships are defined by this rivalry. He is deeply obsessed with surpassing Kamito, whom he sees as a fraud who does not deserve the power he wields. He also has a working relationship with Restia, the dark spirit who was once Kamitos contracted spirit, though this alliance is based on mutual manipulation rather than trust. Over the course of his encounters with Team Scarlet, his arrogance leads to his downfall. He is defeated in battle by Kamito, loses his arm, and is ultimately abandoned by Restia, who erases his memories of Kamito. After this defeat, he is imprisoned in Balsas Prison, the same facility where Claire Rouges parents were held. Still harboring anger over his lost arm, he later convinces members of Team Inferno to break him out of his cell, allowing him to escape into the darkness.

Jio Inzagis abilities are almost entirely dependent on his cursed seal and the spirit Nebuchadnezzar. His primary method of fighting involves using Nebuchadnezzar to draw out and control the seventy-two lesser spirits sealed within his own body. These spirits function as disposable tools; once one is used, he cannot recall or reuse it. Despite this limitation, his fighting style gives him a significant advantage in battle because he can bring forth a variety of spirits all at once, each with different attributes such as wind, lightning, poison, earth, darkness, fire, and even sword and shield types. He also possesses assassination skills, including a technique that allows him to move along any terrain or surface as if it were flat and smooth.