Le Cain is the son of Admiral Gresco and a high-ranking officer within the Gradosian Empire. He is introduced in the second story arc of the series and serves as the main antagonist, as well as the primary rival to the protagonist, Eiji. Appointed as the Supreme Commander of Earth, Le Cain is a ruthless and arrogant individual who firmly believes in the ethnic superiority of the Gradosian people. His driving motivation is to conquer Earth and completely suppress any form of resistance against the Gradosian occupation.

Despite his cruelty and determination to rule, Le Cain possesses a personal code of honor rooted in his self-image as nobility. He refuses to engage in unfair or dishonorable combat, preferring to confront his enemies directly and on equal terms. This sense of aristocratic pride shapes his conduct as a commander and soldier. He is also known to lead a specialized unit called the Demon Death Platoon, which frequently engages in battle against the protagonist's forces.

Le Cain has a notable and complex connection with Julia, who is Eiji's sister. Although he attempts to have her executed for treason, he finds himself unable to follow through with the order because he is strangely drawn to her spiritual force. This internal conflict reveals a layer of vulnerability beneath his otherwise unyielding exterior.

As a character, Le Cain undergoes little change in his fundamental beliefs, remaining a steadfast and prideful adversary throughout his role in the story. He pilots a powerful SPT and is a highly capable combatant, matching Eiji in skill and determination. His role as the main villain places him in direct opposition to Eiji's ideals of peace and coexistence, making their conflict central to the second half of the series.