Uranari, whose real name is Koga, teaches English at the protagonist's middle school in Matsuyama. His nickname "Uranari," meaning "Unripe Calabash" or "Green Pumpkin," alludes to his distinctively pale skin and plump, round face.

Originally from Edo like the protagonist, Uranari possesses a contrasting melancholic and reserved disposition. He exhibits extreme humility and self-effacement, coupled with refined manners and a gentle nature that earn him the protagonist's respect as one of the school's few morally upright figures.

Uranari is drawn into the central conflict through his arranged engagement to the woman known as "Madonna." This engagement attracts the unwanted attention of the manipulative assistant head teacher, Red Shirt, who schemes to supplant Uranari as Madonna's suitor. Exploiting his position, Red Shirt engineers Uranari's transfer to a remote school in Oita Prefecture under the false guise of professional advancement.

Although aware the transfer is Red Shirt's ploy, Uranari passively acquiesces to the reassignment. His departure from Matsuyama effectively eliminates him as a romantic rival. Subsequent reports, like those from the landlady Mrs. Hagino, reveal Uranari's engagement to Madonna was broken off following his transfer, leaving him profoundly unhappy.

Following his transfer, Uranari's role ceases; he does not reappear in the narrative. His fate remains unresolved beyond the known dissolution of his engagement and his unhappiness. No adaptations or supplemental media provide further character development or expanded background beyond the original novel's plot.