Joshua Lundgren is a significant supporting character in the anime GUNxSWORD. He is a young boy of small stature with long blond hair, often dressed in a large ethnic-style garment that conceals a variety of tools on its inside, allowing him to perform maintenance and analysis work on his own. He is first encountered by the protagonists Van and Wendy Garret while they are traveling through a perilous mountain range, where his overly friendly and persistent nature leads him to quickly attach himself to their group, much to the chagrin of the reluctant Van.

Personality-wise, Joshua is defined by a stark contrast between his highly developed technical genius and his profoundly lacking social graces. He is excessively good-natured and honest to a fault, but his most defining trait is a complete inability to read the atmosphere or understand social cues, a characteristic sometimes described as being dense. He speaks his mind without any filter or sense of delicacy, often bringing up uncomfortable topics that others have tried to forget, which sometimes earns him physical reprimands from the group. This lack of social awareness extends to a peculiar obliviousness regarding gender norms, as he has been known to enter women's bathrooms or intrude on someone's shower without realizing he is doing anything wrong. Despite these frustrating traits, he is genuinely kind-hearted and possesses a brave, resilient spirit that prevents him from being discouraged by the harsh treatment he often receives from Van and others.

The core of Joshua's background and motivation is tied to his family. He is the younger brother of Ray Lundgren, a formidable gunslinger also known as Ray Langren, who is consumed by a quest for vengeance against the mysterious Clawed Man for murdering his wife, Shino. Joshua, who also harbored a secret affection for his sister-in-law Shino, wishes for his brother to accept her death and return home rather than continue down a path of murder and self-destruction. He joins Van and Wendy primarily while searching for and trying to stop his brother, a goal that shows his deep love for Ray and his desire to prevent him from becoming a killer, to the point of once physically blocking a bullet meant for the Clawed Man. It is later revealed through Ray's words that Joshua had romantic feelings for Shino, which he kept hidden out of respect for his brother's happiness.

Within the story, Joshua serves an essential role as the group's all-around technical specialist and support operator. His expertise is vast; he acts as a mechanic who helps with the maintenance of the various Armors, a driver for the hover base used for transportation, a combat operator who can assist a pilot with impaired vision, and a skilled hacker capable of disrupting the enemy's sophisticated technology. He possesses knowledge of advanced concepts like space travel, which is rare among the inhabitants of the planet Endless Illusion, allowing him to devise crucial plans for launching the Dann of Thursday into orbit. His skills are not limited to machinery, as he can also assemble improvised weapons like stun guns and timed explosives. Despite his earlier attempts to stop Ray, Joshua evolves to a point of understanding his brother's motives. Following Ray's tragic death in the final battle, Joshua undergoes significant development. He channels his grief into purpose, using his hacking abilities to sabotage the Clawed Man's planetary destruction system, buying Van the precious time needed to destroy it. This act demonstrates his rapid maturation and his determination to ensure that his brother's sacrifice was not in vain. After the final conflict, Joshua expresses his intention to search for the remains of Ray's sunken Armor, Volkain, showing his enduring loyalty to his brother even in death.