Mitsuba's elite older sister. Despite being family, they are not on great terms, as Aoi constantly ignores and gives Mitsuba the cold shoulder, while in turn she more or less holds an inferiority complex towards Aoi for her excellence. When speaking with Shinya in prison, Aoi disparages Mitsuba, calling her a "weakling" and a "traitor", adding that the Sangu family has no place for people like her. Upon meeting with another again, Aoi treats her coldly, and declares that she doesn't acknowledge Mitsuba as a sister anymore after she betrayed them.
Mitsuba knows Shinoa prior to joining her squad, and she is irritated to have to work under her. However, the two girls come to get along and become very close friends. Mitsuba appreciates her honesty, and Shinoa addresses Mitsuba as "Mitsu." They are the only two girls their age in the Moon Demon Company. They later begin causing trouble together and doing pranks on the boys. Although she comes from the prestigious Hiragi family, the family does not support her. Mitsuba acts as her second-in-command.
Mitsuba originally hates Yuichiro for his disobedience and inability to think things through. Shinoa mentions that this behavior reminds Mitsuba of how she used to be before she got her own squad destroyed. They later come to get along. Shinoa teases Mitsuba and says she will fall in love with Yu since they fought so much at the beginning, but Mitsuba denies this. She blushes when they talk, implying that she does have a crush on him.
Mitsuba was not afraid to speak up to him when she disagreed with his choice to put her on Shinoa's squad, which is full of rookies.
Another member of Shinoa's squad. When Mitsuba tells him to call her "Master," he rejects that order. He is skilled at home-making and takes over Mitsuba's job cooking.
A quiet member of the squad. Shinoa and Mitsuba often pretend he is super-innocent and act like they need to protect him from the clutches of Kimizuki and Yu, but they also sometimes blame him for coming up with ideas for their pranks.
Makoto is the leader of his squad in the Moon Demon Company. He fights alongside with Mitsuba and later joins her in Shinoa squad.
Chess defeats Mitsuba and drinks her blood during the battle at Shinjuku. Encountering her again at Nagoya, Mitsuba uses her cursed gear to cover their escape from Chess when they fail to rescue Guren.
Mitsuba has engaged this vampire noble more than once. Though a overwhelmingly powerful foe, Mitsuba still fought where she could, such as using her cursed gear Tenjiryū to try and damage the thirteenth progenitor, and distract him when retreating.
Present on the battlefield at Shinjuka, Mitsuba comes into proximity to this vampire progenitor again at Nagoya.
She witnesses Mika defeat and try and finish off Guren. Later after seeing Mika single handily fight his way through multiple soldiers, including the Moon Demon Armies best, Mitsuba attempts to stop him from reaching Yu but is powerless to prevent Mika knocking her aside.