"Voice Actress's Theater Papaion! Mizuhara-san" centers on the life of Mizuhara, a young and aspiring voice actress navigating the competitive world of voice acting. The story unfolds within the framework of Papaion, a small theater troupe dedicated to producing voice-acted performances. Mizuhara, despite her lack of experience, joins the troupe with a determination to hone her craft and achieve her dream of becoming a renowned voice actress.

The narrative explores Mizuhara's growth as she faces various challenges, including rigorous training, auditions, and the pressures of performing live. Her interactions with fellow troupe members, each with their own unique personalities and struggles, play a significant role in her development. The dynamics within Papaion highlight themes of camaraderie, perseverance, and the pursuit of artistic excellence.

Key characters include Mizuhara's mentor, a seasoned voice actor who provides guidance and tough love, and her peers, who range from ambitious newcomers to jaded veterans. The story delves into their individual journeys, showcasing the highs and lows of their careers and personal lives. Through rehearsals, performances, and behind-the-scenes moments, the series paints a vivid picture of the voice acting industry, emphasizing both its creative rewards and its demanding nature.

The plot balances Mizuhara's professional aspirations with her personal growth, as she learns to overcome self-doubt and embrace her unique talents. The series also touches on the broader aspects of the entertainment industry, such as the importance of networking, the impact of audience reception, and the challenges of maintaining authenticity in a highly competitive field. Overall, "Voice Actress's Theater Papaion! Mizuhara-san" offers an engaging and insightful look into the world of voice acting through the lens of its determined protagonist and her fellow performers.