Chiyoko Fujiwara is the central figure of a story that spans decades of Japanese cinematic history. Her life begins dramatically, born during the catastrophic Great Kanto earthquake of 1923, an event that claimed her father's life and left her feeling as though her existence was traded for his. She grew up in a Japan increasingly dominated by fascist rule, helping her mother run a small sweets shop. As a young girl, she worked as a model for girls' magazines, harboring a quiet hope of finding her own prince charming someday.

In her youth, Chiyoko is portrayed as a timid, shy, and introverted girl. Her life is forever altered when she is scouted by a film studio director, an offer her controlling mother bluntly refuses, dismissing acting as a dubious profession. On that same day, she is accidentally knocked down by a mysterious man fleeing from the police. Despite his desperate situation, he stops to help her up and apologize, an act of kindness that profoundly affects her. She helps him hide from the authorities and secretly allows him to stay in her family's store room.

The man, an artist and political dissident, shares his dreams of a better future for Japan and his hope to one day finish a painting of a snowy landscape. He shows her a skeleton key around his neck, describing it as the key to the most important thing there is, promising to tell her its meaning another time. This chance never arrives, as the police soon discover the man. Chiyoko finds only his key, covered in blood, left behind. Learning he had fled to the train station, she rushes after him but fails to reach him in time. In that moment, she makes a solemn promise to find him and return his key, no matter what it takes.

This promise becomes the single, unwavering motivation of her life. Defying her mother's wishes, Chiyoko enters the film industry, embarking on an acting career that spans several decades. However, her passion is not for the art of cinema itself; rather, acting is a vehicle for her true obsession. She accepts roles and travels to different film sets, including a trip to Manchuria, driven by the belief she may one day locate the mysterious artist. She hopes that if he sees her films, he will recognize her and they will be reunited. Throughout her career, she pours her profound feelings of longing and devotion into her performances, which resonates with audiences and makes her a major star, yet her personal goal remains singular and unfulfilled.

Chiyoko's story is defined by several key relationships. The most significant is with the nameless painter, her first and only love, a man whose face and name she will eventually struggle to remember, but whose memory she chases across her entire life. Her relationship with her mother is one of conflict, representing the traditional path she must reject to follow her own heart. In the film industry, she encounters a persistent adversary: a rival actress who is consumed by jealousy and a mysterious man with a scar on his face, both of who reappear throughout different eras of her films and life, acting as obstacles in her eternal pursuit. Decades later, she is interviewed by Genya Tachibana, a documentary filmmaker and her lifelong admirer, whose arrival and return of her precious key catalyze the flood of memories.

Throughout her long life and career, Chiyoko demonstrates notable development. She transforms from a shy schoolgirl into the strong-willed yet vulnerable star of Japanese cinema. Her personal journey is a relentless, lifelong chase, often described as a pursuit of a shadow. Each role she plays, from a feudal-era princess to a geisha to a futuristic astronaut, becomes a variation of her own story, as she continuously reenacts the act of chasing her lost love across time and space. This intense ability to live her own reality through her fiction is the source of her undeniable authenticity as an actress. Her driving force is the chase itself. It is not until a near-fatal accident on the set of a science fiction film, caused by an earthquake, that she experiences a profound realization. Saved by a young Genya Tachibana, she understands that she is no longer the youthful girl the artist would remember, and she subsequently withdraws from public life and lives as a hermit. In her final moments, she comes to terms with the meaning of her quest, accepting that perhaps the joy was in the pursuit itself, not the destination, and that the key unlocked the memory of him, which was the most important thing to her all along.