After losing half of his family to the nuclear bombing, Gen watches Tomoko die of malnutrition brought on by extreme poverty that plagued Hiroshima's survivors and bears witness to Kimie's painful death of radiation sickness. Meanwhile, he forges new friendships with Ryuta Kondo, a doppelganger of his late brother Shinji; Katsuko and Natsue, two survivors who were scarred by the bombing; Musubi, an acquaintance of Ryuta's when they were in the Yakuza; and Mr. Pak, Gen's Korean neighbor who becomes a successful businessman in Hiroshima's recovery. Gen inspires his friends to rely on their inner strength and remain hopeful in the wake of his town's devastation, using his father's parable about wheat as a vehicle for his own hope.
Gen is loosely based on Keiji Nakazawa, who was himself a survivor of the Hiroshima nuclear bombing.
Kenta Sato, Kazuhide Haruta, and Jun Harada portray Gen in a series of live-action film adaptations released in the 1970s; in the anime films, Catherine Battistone voices Gen in English, and Issei Miyazaki voices him in Japanese; in the 2007 TV drama, Ren Kobayashi portrays Gen as a child and Gaku Yamamoto portrays him as an elderly man.