Voice Range: Mid-Low to Mid-Level Range

Phonon is a senior middle-schooler and Nanase's upperclassmen, Phonon (real name: Yoshiko) was entranced by the rumors of the Hollow Night and sought after gaining abilities for herself. After an encounter with a void and barely escaping with her life, she was soon approached by the student vigilante group known as the EFG who helped inform and train students like her that became in-births. Overjoyed with the fact that the rumors were true, she reluctantly joins the EFG while secretly wishing to simply use her abilities for herself. She heads out into the night to find her true self and play around with her abilities.

Most of the time, Phonon seems very wise-cracking and quick to look down on other people through a harsh and demeaning front. During the Hollow Night, she is forcing herself to act like dominatrix and this sometimes leads to awkward situations.