阿修羅丸

Asuramaru is a high-ranked demon of the Black Demon Series. He formed a contract with Yuuichirou Hyakuya  and became his Cursed Gear.

Asuramaru is a bloodthirsty demon who was originally a vampire. He delights in drinking Yuuichirou's blood and goes into a giddy high after Yuuichirou feeds it to him for the first time. As a possession-type demon, he is described as particularly nasty and aggressive. He also turns very happy when Yuuichirou turns for his help instead of the Seraph gene's.

Like all demons, he is manipulative and uses nightmares to consume the one he possesses in order to take over his host's body. At the beginning of the series, he interrupts his host's dreams every night, making Yuuichirou tired during the day.

After Yuuichirou loosens the curse on him and the two battle for dominance, Asuramaru eventually gives in to his compassion and submits to him. He also stops giving his host nightmares.

Even so, Asuramaru thinks of humans as vile, greedy creatures and says they are even worse than vampires and demons. He considers them to be taboo-breakers who will destroy the world. Although he is fully aware of Yuuichirou going insane on the battlefield and of the experimentation done on him, Asuramaru does not reveal any of these vital secrets to his host.

He considers angels to be disgusting. 

From url=http://owarinoseraph.wikia.com/wiki/AsuramaruOwari no Seraph Wiki