Akemi Hinazuki is the mother of Kayo Hinazuki, and her abusive behavior is a central source of conflict in the story. She is a deeply troubled woman shaped by her own history of suffering, having been in an abusive marriage with Kayo’s father. After divorcing him, she kept custody of her daughter but became estranged from her own family, leaving her isolated. The trauma of her past does not heal; instead, it transforms her into a perpetrator of similar violence. Her cruelty is fueled in part by Kayo’s resemblance to her ex-husband, which serves as a constant reminder of her painful past.

Akemi is portrayed as cruel, unstable, sadistic, and possessive. She regularly beats Kayo, leaving visible bruises, and neglects her basic needs, such as providing proper meals. She punishes Kayo by locking her in an outdoor shack, even in freezing temperatures, and forces her to lie about her injuries to hide the abuse. On one occasion, she dunks Kayo’s head into cold water, claiming it will help wounds heal faster so she will not be blamed. When she goes into town, she dresses up nicely, presenting a normal facade to the world. She is also manipulative and reacts with rage when anyone tries to intervene, attacking Satoru Fujinuma’s mother, Sachiko, with a shovel. Despite her violence, she is a coward who flees from child services rather than face consequences.

Akemi serves as an antagonist, as her abuse creates the desperate circumstances that make Kayo vulnerable to a serial killer. She shows no genuine remorse or development. When her abuse is finally exposed, she has a breakdown, loses custody of Kayo permanently, and is presumably arrested. Her own mother, ashamed of her actions, takes Kayo in. Akemi possesses no special abilities; her power comes solely from her position as a parent, which she uses to wield terrifying cruelty behind closed doors.