"Girlish Number: Momoka Memorial" is a spin-off manga series set in the same universe as the original "Girlish Number" franchise. The story centers on Momoka Sonou, a former child actress turned voice actress, who struggles to find her place in the competitive and often unforgiving entertainment industry. Momoka, once celebrated for her youthful charm and talent, now faces the harsh reality of being overshadowed by younger, more marketable talents. Her career is further complicated by her pride and reluctance to take on roles she deems beneath her, leading to a series of professional and personal challenges.

The narrative explores Momoka's journey as she navigates the complexities of the voice acting world, balancing her desire for recognition with the need to adapt to industry demands. Her interactions with other characters, including her manager, fellow voice actors, and industry professionals, highlight the pressures and politics of the entertainment business. Momoka's relationships with her peers, particularly her rivalry with Chitose Karasuma, a rising star in the industry, add depth to her character and the story.

Throughout the series, Momoka's growth is depicted through her gradual acceptance of her current position and her efforts to redefine her career on her own terms. The manga delves into themes of self-worth, perseverance, and the often harsh realities of pursuing a dream in a competitive field. The supporting cast, including other voice actors and industry insiders, provides additional layers to the narrative, offering insights into the diverse experiences and struggles within the entertainment industry.

The plot is driven by Momoka's internal conflicts and her evolving relationships with those around her, culminating in moments of self-realization and professional development. The series maintains a focus on character-driven storytelling, with a blend of humor, drama, and introspection that captures the nuances of its setting and themes.