The Slacker Is a Sword Saint follows Rune Gladivane, despised as a weakling, who flees into the Dark Forest. There he witnesses Sword Saint Valen's battle with Tiamat, is bathed in dragon blood, and reforges the holy sword, becoming Valen's heir. Ten years later, Rune returns to save his sister Velyna, wins the clan succession trial, and exposes Will's treachery. To protect his clan, he enters the Royal Tournament, defeats powerful foes, earns the title "King's Sword," and meets Princess Sophia. When Archmage Dentine transforms into a black dragon, Rune awakens his true dragon blood, defeats him, and becomes the new Sword Saint.