Asuramaru

The demon residing in Yuuichirou's cursed gear. One of the Black Demon Series. Possession. Materialization. Male. A demon characterized by the appearance of a child with long, purplish-black hair and red eyes. Refers to himself as "Boku."

He possesses the ability "Ashura Kannon," which materializes and releases a sword. When Asuramaru has partially taken over Yuuichirou, he can use techniques that distort dimensions, such as "Mantou Unmei Kousaku." Additionally, he can use "Mugen Tou," which materializes only the scabbard and releases an invisible slash with the drawing command, and "Mugen Battou Unmei Kousaku," which simultaneously stabs the opponent with invisible swords.

A typical demon who despises love and favors desire, he tries to control Yuuichirou by exploiting his desire for power. However, during training, he is taken aback by Yuuichirou's words, "Become my comrade," and reluctantly accepts possession. While he continues to make tempting remarks, he sometimes fights alongside Yuuichirou, saving each other from dire situations.

His former name was Ashera Tepes. He is the elder brother of Krul, who disappeared with the First Progenitor over a thousand years ago. Once a noble during the Dark Ages, he was sold to different slave traders from Krul after their mother was killed by an attack from commoners and was eventually bought by the First Progenitor. He had a good relationship with Yuu, who was with the First Progenitor, but on the night he was summoned by the First Progenitor, he was attacked by Yuu, who had gone berserk after having his power drawn out by the First Progenitor. Ashera was impaled through the heart by Yuu and was taken to the sky, where the First Progenitor beheaded Yuu, causing Ashera to fall. He should have died, but he survived in a near-death state because he had ingested a small amount of Yuu's blood when he was impaled. He was later found by the First Progenitor, who made him ingest a large amount of Yuu's blood, turning him into a vampire as the "third companion allowed to become an elite." At that time, he called the First Progenitor "Shigamadu" following Yuu's example, but later called him "Father" and was considered his favorite.

Although he claims to have no memories from before becoming a demon, he vaguely remembers liking to see the sun and the existence of his sister. After a battle with Shikama Douji, he gradually regains his memories due to the effects of the drugs administered by Yuuichirou, who offered himself as a test subject. When he reunites with Krul through Yuuichirou, he calls her name and smiles.

In reality, he is on the side of the First Progenitor. After fully regaining his memories when the "King" awakens, he plans to restrain the "King" under the First Progenitor's orders, along with Kisekio and Gekkouin.