Mizuki Sonoyama joins Ren's team as its second member in Chapter 8. Years of relentless harassment and bullying during middle school plunged her into severe distress, culminating in her expressing a wish to die rather than endure further torment. After revealing her suffering to Shitara, he employed hypnotic techniques learned from Ren to relieve her accumulated stress. Ren then hypnotized her directly, triggering a profound shift in her self-perception and confidence.

Overhearing a conversation between Shitara and Ren afterward, Mizuki returned displaying a transformed appearance: a new haircut and contact lenses replacing her glasses, marking her internal change. She pledged complete dedication to Ren and Shitara's plan of using hypnosis to liberate humanity from perceived weaknesses. An early chapter silhouette reveals her original hairstyle, shown as Ren discusses forming his team. Her path traces a transition from deep vulnerability to unwavering commitment to the team's mission.