"Koe de Oshigoto!" centers around Kanna Aoyagi, a 16-year-old high school girl who is unexpectedly thrust into the world of voice acting for adult games. The story begins when Kanna’s older sister, who runs a company producing adult content, recruits her to voice a character in an upcoming game. Despite her initial reluctance and lack of experience, Kanna agrees to take on the role, driven by a sense of obligation to her sister and a desire to help the struggling company.

Kanna’s journey into the industry is fraught with challenges. Her naivety and inexperience make the process of recording adult dialogue particularly awkward and embarrassing. She struggles with the explicit nature of the scripts and the pressure to deliver convincing performances. Her mentor, Kouhei Matsunaga, a seasoned voice actor, guides her through the technical and emotional aspects of the job. Kouhei’s professionalism and patience help Kanna gradually overcome her discomfort, though their interactions are often marked by her embarrassment and his teasing demeanor.

As Kanna becomes more involved in the industry, she encounters various colleagues and professionals, each with their own quirks and challenges. The narrative explores the behind-the-scenes dynamics of voice acting, including the technical processes, the collaborative efforts between actors and directors, and the personal growth required to succeed in such a niche field. Kanna’s development is central to the story, as she learns to balance her personal boundaries with the demands of her work, gaining confidence and skill along the way.

The series delves into themes of professionalism, personal growth, and the complexities of working in a sensitive and often stigmatized industry. Kanna’s relationships with her sister, Kouhei, and her colleagues provide emotional depth, highlighting the support systems and challenges inherent in her unconventional career path. The story maintains a balance between comedic moments, stemming from Kanna’s awkwardness and the absurdity of her situation, and more serious reflections on her evolving identity and aspirations.