Akane Sonozaki (園崎 茜, Sonozaki Akane) is the eldest daughter of Oryou Sonozaki and mother to Mion Sonozaki and Shion Sonozaki. She was originally intended to succeed Oryou as head of the Sonozaki family, however her marriage to a yakuza member prevented her from inheriting the family's headship. As such, the position of successor was given to Akane's oldest daughter, Mion.
Akane's history as depicted in all of the media reveals itself in small bits to only later come together. Akane fell in love with an outsider yakuza boss who was neither selected nor approved by the family. When Oryou Sonozaki rejected their union, Akane rebelled. Both enraged, they settled the matter in a spectacular kendo match. Akane was later forced to peel off her fingernail as restitution and lost the right of inheritance. She subsequently gave birth to twin girls, Mion Sonozaki and Shion Sonozaki, and inheritance fell to the eldest of her children, "Mion." As is eventually revealed in the Sound Novel, manga, and anime, Mion and her sister Shion changed places prior to the ceremony where Mion would receive the demon tattoo in recognition of her status. Thus, Shion received the tattoo but took over the identity of Mion while Mion became Shion. There is no indication that their parents or Oryō ever discover this.
Akane still appears at public functions and even acts as a spokeswoman, often with her husband, whose name is never revealed, and whose considerable intelligence contacts have proven very useful to Oryō. Akane's husband is not to be confused with Sonozaki Saburou, who actually works for the Prefectural Assembly and is not part of the yakuza.
Although publicly she cannot be forgiven, Akane told a very young Mion that she and her mother are still very close and friendly in private. As becomes clearer in the later arcs, Akane understands her mother's need for "face": while everyone seems to know that her mother forgave her and even accepts her husband to the point he accompanies her in important meetings, she cannot publicly do so. Thus, after Keiichi Maebara confronts her mother over Satoko Houjou's condition, she wisely advises him to back off to allow her mother the space to act without losing face.
Akane takes over the family after the Great Hinamizawa Disaster. Although technically not able to inherit, she takes power citing that the true successor, her daughter, is still too young to do so. She is later nearly assassinated by a competitor within the group and is badly wounded. She was hospitalized and later died in the hospital where she was treated.