Guren's sergeant and one of squad leaders of the Moon Demon Company. She was sent by him in the beginning of the story to watch Yūichirō when he was tasked with making friends. She is sarcastic and enjoys teasing others, especially Yūichirō. She is the real sister of Mahiru Hīragi who developed the Cursed Gear and despite being part of the Hīragi family, she is uninterested in their power struggle, and is considered a disgrace. Additionally, she is loyal to Guren. She later develops feelings for Yū. Her Demon Weapon is Shikama Dōji (四鎌童子?, lit. Four-Scythe Child), a manifestation-type demon weapon which takes the form of a large scythe, but can be condensed into a pen-like object.

A Lieutenant Colonel and the leader of the Moon Demon Company. He is wise and values teamwork and cooperation, scolding Yūichirō for always acting on his own. He is part of the Ichinose family, a low branch of the Hīragi family, and is thus belitted by the high-ranking members of the family. He plans on dethroning the Hīragi family. He was Mahiru Hīragi's lover, but when her experiments led to her become insane and transform into a demon, he killed her. His Demon Weapon is Mahiru-no-Yo (真昼ノ夜?, lit. Midday's Night), a possession-type demon weapon which takes the form of a katana and Mahiru herself.

When Yūichirō (also known as Yū) was twelve years old, he and his best friend and fellow orphan Mikaela plotted a plan with other children from the Hyakuya Orphanage to escape the vampires' captivity. However, their plan was foiled by Ferid Bathory, who then slaughtered his "family" and presumably Mikaela, who urged Yū to run away, a fact he regrets to this day. One of Yūichirō's driving forces is his need to destroy all vampires for what they did to his family, yet he doesn't allow revenge to consume him and instead chooses to become strong for his new family's sake. He enlisted in the Japanese Imperial Demon Army for vampire extermination, the Moon Demon Company. He is not always a good team player, but is kind and caring deep inside. His Demon Weapon is Ashuramaru (阿修羅丸?), a possession-type demon weapon which takes the form of a katana.