Content Warning: Confessions depicts extreme bullying, child abuse, murder, mental health crises, a bombing, and murder-suicide. The text contains some stigmatizing language surrounding HIV/AIDS and the misgendering of a character; this guide reproduces such language only through quotations.

Moriguchi, a middle school science teacher, takes on a god-like quality in the story given her relative omniscience of events and the careful control she exhibits throughout the narrative. Depicted as careful and considerate, but also vengeful and realistic, Moriguchi is the character who is most aware of her own actions—she actively chooses to exact revenge on the students who killed her child by putting blood in their milk, even though she knows it is a crime. Although she ostensibly retires, her presence remains in the classroom not just as a foil for Werther (an inferior teacher) but also through her manipulations of the classroom chaos and bullying through him. While she can’t predict everything—particularly Mizuki’s suffering and death, which is her only regret—she remains in control of the psychological torture she induces, ultimately engineering the death of Shūya’s mother at his own hands.

Despite her unconventional family—she is a single mother whose ex-fiancé, Sakuranomi, is dying from AIDS—she is a thoughtful and considerate mother, the most nurturing of the three presented in the novel.