The characters of Yukio Mishima's Sun and Steel are not novel-like characters in the sense that they are not well developed, they do not drive a plot, and they are not named. Mishima's novel-length essay (published in 1968 and translated to English in 1970) discusses the author's relationship with his craft as a writer and his regimen of weight training, as well as the intersection between the two. The characters are those whom Mishima meets amid his alternate trajectories as a writer and bodybuilder.

First, Mishima's composition teacher influences him. Mishima explains that his teacher did not like his work, for the reason (suspected by Mishima) that he was too precocious a writer. Specifically, he know from a young age the power of words to distort reality. Therefore, his writing was not realistic. In a way, this teacher (who, like other characters, appears only briefly) influences Mishima by (ironically) alerting him to his writing acumen.

Next, Mishima witnesses a group of people carrying a portable shrine in the streets. This is Mishima's first exposure to individuals who partake of physical activity that is distinct from the mental and intellectual. Years later, Mishima explains, he would emulate these young men by carrying a shrine in such a festival.

Later, Mishima experiences a somewhat depressive state after the summer of 1945 (at the end of World War II). He leads a nocturnal existence, reading the work of Novalis and Yeats and keeping the company of a literary circle that was similarly disposed. The members of this group (all unnamed) have "sagging stomachs" that is evidence of their nocturnal thinking, and, though Mishima spent his boyhood living a lifestyle of the mind instead of body, he would turn himself to the latter for the next ten years.

Finally, in his epilogue, Mishima joins a pilot in an F104 plane. Mishima is seeking a point where the extremes of the body and spirit are joined. The pilot receives instructions in English and explains to Mishima their altitude (reading forty-five thousand feed), speed (the speed of sound), and location (as they fly nearby to Mt. Fuji). Mishima thinks to himself that the plane is like a phallus piercing the sky. Arguably, the taciturn and underdeveloped figure of the pilot operates metaphorically as a sexual partner.