First-year Japanese major Yuu Sasaya is a naive country girl who has yet to adjust to the sophisticated city lifestyle. After watching a stage play for the first time, a particular minor role's performance leaves such a profound impact on her that she decides to pursue a career in acting.

Yuu confesses her newfound dream to a classmate and though ridiculed, attains an opportunity to tour a theatre company. While there, she meets the well-reputed rookie actor, Touya Ichii, and immediately recognizes his voice as the character who had impacted her. Seeing Yuu's passion, Touya recommends her to his friend's troupe, Garandou Company, run by Shougo Shimamura.

Shougo tests Yuu's acting skills with high expectations, only to discover that she is a complete amateur. Unwilling to accept defeat so soon, she pleads him to let her observe and learn from them over time. Ashita no Ousama tells Yuu's story as she searches for her hidden flair among the different positions offered in a theatre troupe, with immense determination to make it big in the world of the dramatic arts.