Dan Lang is a young boy of approximately eight years old who lives with his older sister, Doris, on a farm in the frontier town of Ransylva. He is the son of a deceased werewolf hunter, and after his father’s death, the farm and the responsibility for Dan’s upbringing fall to Doris. In the original novel and its film adaptation, Dan is depicted with brown hair and blue eyes, while his appearance in the animated movie gives him dark brown hair and a cross necklace. He is a skilled young farmer, knows how to use a rifle, and is capable of operating his home’s security system to defend against the wandering beasts that plague the frontier.

Dan’s personality is defined by a fierce protectiveness and a determination that often exceeds his young age. He deeply loves his sister and is intensely loyal to her, refusing to see her harmed or disgraced, even when the town turns against her after she is bitten by the vampire Count Magnus Lee. This protective instinct manifests in a stubborn bravery; he is not afraid to stand up to adults, such as the mayor's son Greco Rohman, and he threatens them with a rifle to defend his family's honor. Though he is sometimes driven by emotion and his actions can land him in trouble, Dan’s primary motivation is to take care of his sister himself and ensure her safety, believing it to be his responsibility as the man of the house.

Within the story's central conflict, Dan serves as both a motivator and an active participant. His presence raises the stakes for his sister Doris and the vampire hunter D, as Dan's safety is one of Doris's primary concerns when she hires D. Initially, Dan is frightened and cries when faced with the danger posed by Count Lee, but he is encouraged by D, who tells him he must be strong for his sister's sake. This moment forges a key relationship for Dan, who begins to look up to D as a role model, despite the townspeople’s distrust of the mysterious dhampir. Dan does not remain a passive child in need of rescue; he takes an active role in the climax, firing a gun at Greco and even attempting to confront Count Lee directly to save Doris, showing his immense courage.

Dan’s most significant relationships are, of course, with his sister Doris and with D. His bond with Doris is one of mutual devotion, as she is willing to harm herself to protect him, and he is willing to face vampires for her. His relationship with D evolves from initial curiosity and a demand for protection into a profound respect. D makes a promise to Dan that he will protect them, a promise he keeps, and this act solidifies D as a heroic figure in the boy's eyes. Over the course of the narrative, Dan undergoes notable development. He begins as a frightened child, but the harrowing events force him to mature rapidly. A key moment of his development occurs after the final battle; when Doris weeps over D’s departure, a young Dan comforts her, vowing to take care of her and the farm. He is no longer seen as just a little boy, but as someone capable of bearing great responsibility. It is said that years later, he grows into a young man who helps his sister as a true adult would. In terms of notable abilities, Dan is proficient with a laser rifle and is knowledgeable about the farm's defensive systems, skills necessary for survival in the harsh frontier. He is also resourceful, using his childhood knowledge of the local forests to navigate shortcuts when he sets out alone to save his sister.