"Million Doll" centers on the world of underground idols and the impact of social media on their careers. The narrative revolves around Riko, a socially awkward young woman with a unique ability to make any idol she promotes go viral through her online presence. Despite her talent, Riko harbors a deep disdain for the idol industry, stemming from a personal grudge against a popular idol named Yua. Riko's motivations are driven by a desire to prove that her online influence can elevate lesser-known idols to stardom, challenging the dominance of established figures like Yua.

The story introduces a struggling idol group called "Million Doll," which consists of three members: Itorio, Non, and Marina. Each member faces their own challenges, from lack of recognition to personal insecurities. Riko takes an interest in the group, seeing them as the perfect candidates to test her promotional skills. As she begins to support them, the series explores the dynamics of the idol industry, the pressures of fame, and the ethical dilemmas of manipulating online popularity.

Riko's interactions with the idols and her rival, Yua, reveal the complexities of their relationships. Yua, once a close friend, represents the success Riko feels she was denied, creating a tense dynamic between the two. The narrative delves into themes of ambition, jealousy, and the consequences of seeking validation through social media. As Riko's efforts to boost Million Doll's popularity intensify, the series examines the fine line between genuine talent and manufactured fame, as well as the personal sacrifices required to succeed in the competitive world of idols.

The characters are portrayed with distinct personalities and motivations. Riko's pragmatic and often cynical outlook contrasts with the idealism of the idols she supports. Itorio, the leader of Million Doll, is determined and hardworking, while Non and Marina bring their own quirks and struggles to the group. Yua serves as a foil to Riko, embodying the success and recognition that Riko both envies and resents.

The plot progresses through a series of promotional campaigns, live performances, and personal confrontations, highlighting the challenges faced by both Riko and the idols. The series balances moments of humor and drama, offering a nuanced portrayal of the idol industry and the individuals who navigate it. Through its exploration of online influence and the pursuit of fame, "Million Doll" provides a thought-provoking look at the intersection of technology, ambition, and human connection.