Gen Kurai, who also goes by the name Dromus, is a central figure whose journey from solitary antagonist to valued ally forms a key arc within his story. He is a mysterious transfer student who arrives at the same school as the main protagonists, but this ordinary exterior conceals his identity as a Tenkai Knight who serves the initial primary villain.

Physically, Gen appears to be around thirteen years old, possessing red eyes and styled auburn hair with long bangs that often cover one eye. His typical attire consists of a black, high-collared jacket and matching pants, which gives him a consistently aloof and guarded appearance. His counterpart on the world of Quarton, named Dromus, is the Black Knight, a warrior whose grey and black armor strongly resembles that of the hero Bravenwolf, save for a distinct scar on the left eye of the wolf emblem on his chest plate. In this form, his own eyes also glow red. Later, after joining the heroes, Dromus gains new transformations, including a Phoenix Mode where his grey armor turns gold and his eyes become green, and an Elemental Mode known as Dromus Tenkai Whirlwind, where his eyes turn blue and he commands elemental wind powers.

At the outset, Gen's personality is calm, cool, and collected to the point of being distant and dismissive. He openly expresses disdain for those who rely on teammates, viewing such dependence as a sign of weakness. However, this hardened demeanor is not his original nature. It is revealed that he was once a positive and outgoing child, similar in spirit to the hero Guren Nash, but his life took a tragic turn following the loss of his parents. This event, and his subsequent path, led him to be given the Dromus Core Brick by a being named Eurus and eventually serve the evil Vilius, all while harboring his own secret ambitions for power.

Despite his role as an antagonist, Gen's motivations are not purely malicious but are rooted in his personal pain and a desire for control. As Dromus, he carries out Vilius's orders, such as using a device called a Core Corrupter to turn allies evil and hunting for the powerful Dragon Keys. Yet, he simultaneously operates as a student on Earth, where he engages with the heroes in a more subtle manner. He is intensely curious about Guren, whom he suspects of being his enemy Bravenwolf, and even offers him cryptic advice about choosing which side of a coin to be on, a lesson that ultimately helps the heroes in battle. This dual existence highlights his internal conflict and positions him not as a straightforward villain but as a wild card.

His relationships are the primary catalyst for his development. His rivalry with Guren Nash is central; Guren continuously tries to understand and sway Gen from his dark path, seeing the good within him. This persistent belief from his enemy, combined with a lecture from his former ally Beni and witnessing the other Knights' unwavering struggle against evil, leads Gen to a moment of epiphany. In a significant turning point, he betrays Vilius directly, jumps into the fray to help the Tenkai Knights, and aids in restoring peace to Quarton. After this, he sheds his role as a spy and becomes an official, if initially distant, fifth member of the Tenkai Knights.

As a warrior, Gen possesses considerable skill and intelligence. He has a habit of proving himself to be a cut above his peers in various disciplines, often demonstrating mastery in activities like basketball and chess that the other heroes are known for. On the battlefield as Dromus, his signature ability is his control over wind, making him a swift and agile fighter. His power progression mirrors that of the other knights, as he is shown to unlock advanced transformations such as Titan Mode, Elemental Mode, and eventually Elemental Titan Mode, solidifying his place as a powerful and equal member of the team.