Guren Ichinose

Race: Human
Namanari
Age: 24
Birthday: August 28, 1996
Height: 183 cm (6'0")
Weight: 65 kg (143 lb)
Blood type: O
Rank: Lieutenant Colonel
Section: Moon Demon Squad
Affiliation: Japanese Imperial Demon Army
Demon Weapon Series: Black Demon
Demon: Mahiru-no-Yo

The demon Mahiru-no-Yo was once a human named Mahiru Hiiragi and is the love interest of Guren Ichinose. She was also the next successor to the main house until she turned into a demon.

Guren Ichinose is the main protagonist of the Owari no Seraph: Ichinose Guren, Jyuurokusai no Catastrophe series and an important character in the Owari no Seraph series. He is a Lieutenant Colonel of the Japanese Imperial Demon Army and the commanding officer of the Vampire Extermination Unit, Moon Demon Company.

(Source: Owari no Seraph Wikia)