Dan Simmonds is a key supporting figure in Argento Soma, serving as the pilot of the combat unit known as Zark 1 and holding the position of an ace within the military organization Funeral. His background is marked by a privileged but troubled upbringing, as he was born into a prominent British aristocratic family. This heritage, however, became a source of deep personal conflict. Driven by a rebellious spirit against his family’s history, particularly his mother's suicide and his father's perceived helplessness in the face of such tragedy, Dan rejected the path laid out for him. He famously refused to live what he considered a cowardly life like his father, choosing to abandon his family estate and join the ranks of Funeral, effectively severing ties with his noble lineage.

In terms of personality, Dan is initially presented as a confident and skilled individual, embodying the cool-headed demeanor expected of an elite operative. However, he possesses a distinct stubborn streak and a strong sense of personal justice, which often puts him at odds with others. His most significant early friction is with the protagonist, Ryu Soma, whose mysterious past and unorthodox presence threaten Dan’s established standing within the group. This rivalry is not merely about professional competition but also a clash of fundamental approaches and personalities. Over time, as they are forced to cooperate through various missions and even share a period of confinement together, Dan's rigid stance softens. He gradually moves past his initial animosity, learning to respect Soma as a dependable comrade rather than viewing him as a rival.

Regarding his role and relationships, Dan is a core member of the Funeral team under the command of Captain Michael Heartland. His abilities as a pilot make him an essential asset in the group's battles against the alien entities known as the "Unknown." A significant relationship in his life is with his sister, Elaine, who personally sought him out in an attempt to bring him back to the family fold, highlighting the personal costs of his chosen path. His character arc shows considerable development; he evolves from a hotheaded rival into a mature and reliable leader. By the conclusion of the series, Dan succeeds Ines as the commander of Funeral, accepting a position of great responsibility. He also settles into a personal life, marrying his colleague Sue Hawkins. In a poignant tribute to a fallen friend, he names his child after Guinevere Green, a fellow pilot who was killed in action. His notable abilities center on his exceptional skills as a mecha pilot, specifically his mastery of the Zark 1 unit, which cements his status as one of Funeral’s most formidable fighters.