Yan manages operations at her family's yakitori restaurant alongside being Myon's elder sister. Her family history is marked by her father's past involvement with the yakuza, specifically his role in seducing away the mother of a senior yakuza figure during their youth.

When yakuza seeking retribution against her father violently confront the family at the restaurant, Yan witnesses both her sister Myon's near-rape and Nishi's initial death. Following Nishi's unexpected return to life and subsequent actions, Yan flees with Nishi and Myon in a stolen yakuza car, culminating in a chaotic plunge off a bridge that traps them inside a whale.

Initially confined within the whale alongside the others, Yan undergoes personal development, shifting from a peripheral role to a more prominent and creatively engaged presence. She dedicates substantial time in isolation to deeply explore new interests, practicing dance and creating art.

As the whale's health deteriorates and internal waters rise, Yan collaborates with Nishi, Myon, and the whale's resident old hermit to devise an escape. She participates in constructing a motorized boat using salvaged components from the yakuza car. Yan successfully escapes the whale alongside Nishi, Myon, and the old man when it resurfaces near Osaka.

Her character arc concludes within the film's broader montage reflecting on choices and possibilities, emphasizing life's journey as an ongoing process.