Masumi is a young woman who appears in the fifth episode of Mushishi Zoku Shou, the second anime season known in English as Mushishi: The Next Chapter. She is a supporting character encountered by the traveling mushishi Ginko during one of his journeys. She has black hair that falls to her shoulders and black eyes, and she lives in a rural village typical of the series' historical setting.

Masumi's personality is defined by a tendency to fall in love quickly and deeply. However, she is also portrayed as emotionally fragile: after experiencing heartbreak from a lover who abandoned her, she becomes passive, withdrawn, and hesitant to engage with the world around her. Her initial cheerful and open demeanor gives way to a guarded and melancholic state. Her primary motivation in the episode is to cope with the pain of rejection and to find a sense of closure or peace.

In the story, Masumi's role is to illustrate how human emotions can become entangled with the mysterious mushi that inhabit the natural world. Ginko's investigation into her condition reveals that her emotional turmoil has been exacerbated or reflected by a mushi, leading to a phenomenon that affects her perception or behavior. Her relationship with Ginko is that of a client seeking help, and through his intervention she gains a deeper understanding of her own feelings and the natural forces at play.

Masumi does not exhibit any unique abilities related to mushi; she is an ordinary human whose ordinary emotional struggles intersect with the supernatural. Her development within the episode involves moving from a state of passive heartbreak toward a tentative acceptance of her past, allowing her to begin healing. She has no other known appearances in the series, making her a one-episode character whose story contributes to the overarching theme of the delicate balance between human life and the unseen world of mushi.