James Carthew is the president of the Solar Federation in the anime Captain Future. He is the leader of Earth's government and the highest political authority within the federation, based at its central headquarters on Earth. He first appears in the fifth episode, titled "The Greatest Danger of the Solar System," when he is kidnapped by space pirates who intend to force the Solar Federation to surrender to their demands. His capture demonstrates how central he is to the political order of the solar system, and the episode establishes the pattern of the federation's leadership relying on outside help when crises exceed the reach of ordinary law enforcement.

As president, Carthew is responsible for the security and protection of the entire solar system. He frequently faces difficult decisions about how to respond to threats from criminals and hostile forces. He is intelligent and tactically minded, making use of all the resources available to him to counter the plans of the various villains who menace the federation. His leadership style is rational and practical; he is confident, decisive, and willing to take calculated risks when the safety of the federation requires it. He holds strong principles, expects a great deal of himself and those around him, and is focused on justice and integrity in the exercise of his office.

Carthew's motivations center on preserving the stability and safety of the Solar Federation. He is not driven by personal ambition but by a sense of duty to protect the worlds and citizens under his authority. When threats arise, he is prepared to make hard choices, including summoning exceptional individuals whose methods go beyond standard procedures.

In the story, Carthew serves as a recurring supporting character who sets many missions in motion. He is the official who calls upon Curtis Newton, known as Captain Future, in extreme need, giving the hero and his companions the authority to act against dangers that threaten the solar system. In this way he functions as a bridge between the federation's government and the unconventional heroes who operate outside it. He is also the superior of Planet Patrol agent Joan Randall and space marshal Ezra Gurney, both of whom answer to him in matters of intersolar security.

His key relationship is with Captain Future. Carthew trusts the hero completely in moments of crisis and repeatedly relies on his scientific knowledge and combat abilities to resolve situations the authorities cannot handle alone. His relationship with Joan Randall and Ezra Gurney is more formal, as they are officers under his command, but they share the same commitment to protecting the federation. When Carthew is captured, the effort to rescue him ties together the main characters and underscores his importance to the federation's functioning.

Carthew's personal development over the course of the series is modest. He remains a consistent and stable figure of authority rather than undergoing a dramatic personal transformation. His experiences, particularly being taken hostage, tend to confirm his belief that extraordinary threats require extraordinary defenders, and they deepen his reliance on Captain Future and his team.

Carthew's notable abilities are political rather than physical. He possesses no special combat or scientific powers; his strengths lie in leadership, strategic and tactical thinking, and the ability to coordinate the resources of an entire federation. He is an effective decision-maker under pressure, and his calm, principled demeanor gives the government of the solar system a credible and respected face. Through his authority and judgment, he plays an essential part in enabling the heroes to do their work.