OVA
Description
Dan Lang is the younger brother of Doris Lang and a resident of the frontier town of Ransylva. He is the son of a deceased werewolf hunter, and he lives with his sister on their family farm. His age is typically described as eight years old in the primary source material, though some references mention him as twelve.

In terms of personality, Dan is an inquisitive and determined boy who displays a maturity beyond his years. He is fiercely protective of his sister, Doris, and his primary motivation throughout the story is to ensure her safety after she is bitten by the vampire Count Magnus Lee. Although he is young, he believes he should be the one to take care of Doris and does whatever he can to help her, even when his actions put him in danger. He is portrayed as being brave enough to stand up against adults, including the mayor's son, Greco Rohman, and even attempts to attack Count Lee directly to save his sister. He has a great fondness for the vampire hunter D, looking up to him as a role model despite knowing he is a dhampir, and he does not fear or hate him for his nature.

Dan's role in the story is that of a supporting character whose vulnerability serves as a key source of tension. He is frequently perceived as Doris's weakness, and the antagonists attempt to use him as leverage against her and D. He is kidnapped by the servant Rei-Ginsei and used as bait to lure D into a trap. However, Dan is not merely a passive victim; he demonstrates resourcefulness by knowing how to use a rifle and operate the farm's security system to defend against wandering beasts. When he is left alone after his sister is taken to Count Lee's castle, he arms himself and navigates the dangerous Ransylva Forest using shortcuts he learned as a child, determined to save her himself when he believes no one else will.

Dan's key relationship is with his sister, Doris. He is deeply attached to her and refuses to be separated from her, protesting when a family offers to take him in after the townspeople decide to send Doris to an asylum. He also shares a significant bond with D. D shows a degree of kindness to Dan that he rarely displays with others, kneeling to make a promise to the boy that he will protect him and his sister. D also encourages Dan to be strong and not to cry, telling him that he is already a man. In return, Dan is loyal to D and seeks his approval. At the end of the story, Dan wears a blue pendant given to him by D, and he comforts a crying Doris by vowing to take care of her and the farm, demonstrating that he has internalized D's lesson about strength and responsibility.

Throughout the narrative, Dan undergoes a subtle but clear development from a frightened, crying child into a more resolute and dependable individual. While initially seen crying outside a store, he is later described as no longer being a little boy when he comforts his sister and promises to protect her. After D departs, Dan assumes the role of caretaker, laughing despite his sadness and showing that he is ready to fulfill the promise he made to his "big brother" D.

Dan's notable abilities include his proficiency with a laser rifle and his familiarity with operating technological defenses. He also possesses a working knowledge of the local terrain, which he uses to traverse the forest in his attempt to rescue his sister. He is also shown to be capable of riding a horse.