In 2071, toxic air pollution had devastated the world, leaving only 1% of the population alive. People rarely leave their homes without gas masks, and delivery drivers known as knights protect and deliver packages. One legendary knight, Knight 5-8, meets a young refugee named Sa Wol who dreams of becoming a knight. With the help of Seol A, an officer in the Defense Intelligence Command, Knight 5-8 trains and mentors Sa Wol, helping him achieve his dream in a dangerous and harsh world.