"Cinderella Express" centers on a young woman named Rika, who works as a maid in a luxurious hotel. Her life takes an unexpected turn when she encounters a mysterious guest, a wealthy and enigmatic man named Shoma. Shoma, intrigued by Rika's diligence and kindness, offers her a unique opportunity: to act as a temporary companion for his younger brother, Kaito, who is struggling with personal issues. Rika reluctantly agrees, setting the stage for a complex dynamic between the three characters.

As Rika becomes more involved with Shoma and Kaito, she discovers that their family is entangled in a web of secrets, power struggles, and unresolved emotional conflicts. Shoma, the elder brother, is a calculating and ambitious businessman who often hides his true intentions behind a polished exterior. Kaito, on the other hand, is more vulnerable and rebellious, harboring resentment toward his brother and the expectations placed upon him. Rika's presence begins to challenge their relationship, as she becomes a bridge between the two brothers, forcing them to confront their differences and shared past.

The narrative explores themes of class disparity, personal growth, and the complexities of familial bonds. Rika's journey is marked by her efforts to navigate the opulent yet isolating world of the wealthy, while maintaining her own sense of identity and integrity. The series delves into the emotional struggles of each character, revealing layers of vulnerability beneath their outward personas. As the story progresses, Rika's role evolves from a mere observer to an active participant in the brothers' lives, ultimately influencing the trajectory of their relationship and her own future. The interplay between the characters drives the plot, creating a blend of drama, romance, and introspection.