Mihari Oyama

Mihari Oyama is a scientist and Mahiro's younger sister in Onimai. Concerned by Mahiro's isolated adult life, she administers an experimental drug that changes Mahiro into a younger girl and supervises the resulting return to school and society.

Mihari Oyama behind Mahiro's transformation

Intelligent, controlling, and genuinely caring, Mihari sometimes treats her sibling as a research subject. Her methods are ethically questionable, but her goal is to restore health, routine, and human connection.

Scientific control, sibling concern, and the ethics of forced rehabilitation

Mihari's expertise includes biology, chemistry, and continuous monitoring of the transformation. Her relationships with Mahiro, Kaede, and the younger friend group make her both guardian and source of the central identity disruption.