Though they are sisters, Aoi and Mitsuba are not on good terms with one another. Aoi normally gives her the cold shoulder, and ignores her hourly. One example of this is when she arrived at Nagoya Airport with Kureto, Aoi notices her younger sister but turns her head from her, and does not say a word. Later, when she talks to Shinya in prison, she claims the Sangu clan has "no need for weakling and traitors" like Mitsuba. Further, once they meet again after Mitsuba's departure from the JIDA, Aoi makes it clear that she does not acknowledge Mitsuba as a sister anymore after betraying them in her mind.
Aoi is Kureto's personal assistant, and is extremely loyal to him. She follows his orders without question, and even agrees when Shinya calls her Kureto's pet. She secretly has a crush on him, however he is unaware of it.
She meets him while he is in prison, and tells him to "act like a Hiragi". In anger he simply calls her Kureto's pet, which she agrees with.
Aoi went to high school with him during their time as teenagers, although they did not interact too much.
He is the head of the Hiragi family. He threatens to keep Aoi as a hostage if Kureto does not obey his orders.
A member of the Hiragi family and when he threatens to inform Tenri of Kureto's plans, Aoi takes Kureto's side in the matter by killing his guards.
A black demon-wielder under Guren's command. He attempts to strike at Kureto from behind with Aoi blocking the attack but says he is strong.