This article examines how a major twentieth-century Korean writer, Kim Tongin, adopted the language of Western medical science to produce the effect of literary interiority as an iteration of the individual in his novella “Oh, the Frail-Hearted!” (1919–20). My reading of the story unravels the ways in which this work draws several equations between the practice of medical science and that of literature. The main character’s diary and letter are treated as his medical records; a well-known man of letters acts as his doctor by identifying his symptoms through the “medical” gaze; readers are invited to read his “mind” the way doctors examine those of their patients; his illness gives his interiority an identifiable form; and his extramarital affair is not only a love story but also a trigger of his mental illness. The medical gaze allows him to explore his sexuality beyond the traditional conjugal norm—whether via a heterosexual love affair or homoeroticism. His pursuit of individuality is, however, bounded by the “colonial” gaze, under which he appears as an accomplice of the collective debilitation of the colony through a moralistic prism.