Lex Hiyama, whose full name is Ren Hiyama, is the owner of the coffee shop Blue Cats and a member of the shadowy organization known as Seeker. He is widely recognized as a legendary LBX player, piloting the powerful G.Rex model. In the early part of the story, Lex presents himself as a calm and collected supporter of the main protagonist Ban and his friends, offering guidance and assistance from the background. However, as the first season progresses, his true role is revealed: he is the mastermind behind the Yoshimitsu Kaidou android, having taken the Innovator's original plans and twisted them to serve his own personal vendetta.

Lex's motivations are rooted in a tragic past. His father died, and the ensuing scandal caused his family to be ostracized and eventually scattered. This loss and the resulting isolation fuel a deep-seated desire for vengeance, driving him to manipulate events from the shadows. His personality is characterized by a cool, analytical demeanor and a strategic mind, but beneath that exterior lies a simmering resentment and a willingness to use others to achieve his goals. He is not inherently malicious but rather a product of his circumstances, making him a complex antagonist rather than a simple villain.

His key relationships are primarily with the main cast, particularly Ban, whose own father is connected to the LBX technology Lex exploits. Lex's interactions with the Innovator organization are also central, as he co-opts their resources for his own ends. Throughout the narrative, Lex undergoes significant development as his carefully laid plans are challenged and he is forced to confront the consequences of his actions. His abilities extend beyond expert LBX piloting to include advanced technical knowledge, strategic planning, and the capacity to orchestrate complex schemes involving artificial intelligence and robotics. Lex Hiyama stands as a formidable and nuanced figure whose personal tragedy and calculated choices shape a major arc of the series.