Tsubasa Ono, also known as Tsubasa Onodera, trains as a voice actress at the Lambda Eight school alongside four peers: Momoko Ichihara, Rinka Suzuki, Yurika Sasaki, and Amane Ōhara. A self-identified tomboy, Tsubasa exclusively pursues male voice acting roles, setting her apart from classmates voicing female characters. This focus shapes her initial professional approach.

Her development involves stepping outside her comfort zone. She explores traditionally feminine expressions during a practice date with an admired senior, framed as professional development for female role practice. This experience broadens her skills without shifting her primary career goal towards male roles.

Tsubasa and her peers face shared challenges, including financial struggles at Lambda Eight. When the school faces bankruptcy, they form the idol unit "Sister x Sisters" for a crucial promotional performance. The unit's success helps sustain the school, showcasing Tsubasa's adaptability within an ensemble despite her specialization. Her documented background and development occur solely within the core 25-episode series.