Mizuki Usurai is a cheerful second-year student at Sumomogaoka High School who presides over the Broadcasting Club. Her defining trait is immense enthusiasm for club activities and objectives, driving her persistent recruitment efforts, like coaxing Hana to join and compelling Hakoyama to compete. Leadership motivates her actions, though she exhibits moments of stubborn insistence.

Her leadership style is spontaneous and impulsive. During broadcasts, she frequently abandons scripts to improvise. This tendency extends to practices, where she displays impatience with fundamental drills, as noted by Ryouko. A degree of informality, bordering on impoliteness, colors her interactions with the club advisor. Despite this, her passion fuels the club's ambitious goals, specifically reaching the national tournament finals.

Mizuki's pivotal role involves recognizing and recruiting talent. After observing Hana's skill at engaging listeners through storytelling, she relentlessly pursues Hana for the club. Witnessing Hana recite "An Asura in Spring" during an emotional, rain-soaked moment solidifies Mizuki's belief in Hana's potential and strengthens her resolve. She persuades Hana by focusing on helping her discover her identity through recitation.

Within the club, Mizuki operates alongside vice president Ryouko Totonoi and advisor Hiromi Kichijouji. She spearheads orientation sessions, facilitates member introductions, and oversees competition preparations, including guiding category selections and conducting vocal exercises. Her leadership directly shapes the club's direction and collective aspirations.