Riko is a lonely and deeply troubled teenage girl living in Hokkaido in 1990. Marked by her vivid red hair and a profound depression, she harbors a strong death wish and a hatred for her city, her school, and a world she sees as corrupt and meaningless. This secret desire for the annihilation of all she despises leads her to occasionally dress provocatively to imply engagement in sex work, a behavior stemming from self-hatred. When a dragon is shot down by military forces, Riko takes its egg. It hatches into a baby dragon, which she names Carmine, intending to raise it as an instrument of destruction to fulfill her wish. She cares for the dragon in an abandoned building, feeding it to build its strength. Her perspective shifts when the rapidly maturing Carmine reveals the true nature of the conflict: the dragons are humanity's protectors, and the real threat is an invasion of demons from another dimension. Confronted by this reality and the immediate demonic threat that manifests by possessing humans, Riko recants her desire for annihilation and begs Carmine to help save humanity. To protect her, Carmine breaks off one of his own horns, which repels demons. During the final confrontation with the materializing Demon King, who takes on Riko's appearance, she makes the ultimate sacrifice. Ignoring Carmine's pleas, she leaps from his back and impales the demonic entity with the dragon horn. As she falls to her death, her final words are a plea for Carmine to remain as Earth's protector, and she comments on the beauty of the natural world.