Kubernes is a male adult pirate mercenary who serves as the central antagonist in the anime. He operates entirely alone aboard his personal vessel and is defined by his willingness to carry out any task as long as the compensation is sufficient. His physical appearance includes short brown hair, blue eyes, and a distinctive eyepatch often accompanied by a headband. One of his defining features is a metal arm, which incorporates a range of modifications that make it a formidable weapon and tool, and he does not hesitate to eliminate anyone who obstructs his path.

Personality-wise, Kubernes is coldly pragmatic, independent, and ruthless. He approaches situations with a strategic mindset and a dominant, self-reliant attitude, rarely acknowledging the input of others. Although he can display a certain professional dedication and even a surface-level concern for those he takes under his wing, these moments are typically overshadowed by his overriding mercenary nature. He is quick to anger when challenged and deeply stubborn, refusing to compromise once he has set a course of action. At his core, he is driven purely by financial gain, and this single-minded motivation dictates all his choices.

Within the story, Kubernes enters the narrative as a dangerous wild card. He rescues the soldier Vestemona Lauren after she is left adrift at sea, informing her that she has been declared dead by the Earth Forces. He then promises to teach her how to pilot a Round Buckler from within, acting as a temporary if severe mentor. However, his student soon grows impatient with his methods, and the arrangement dissolves. Kubernes later emerges as the primary rival in the hunt for the Stone of the Gods, culminating in a direct duel with the protagonist Gram over the artifact. Throughout the series, his role is that of a formidable obstacle—skilled, unpredictable, and motivated by the highest bidder.

Kubernes’s abilities center on his exceptional Round Buckler piloting skills and the lethality of his augmented arm. He is a veteran combatant and a precise tactical thinker, capable of holding his own against multiple opponents. While the series does not explore his past in depth, his proficiency and solitary nature suggest a long and harsh career as a hired gun in the flooded world. Though he undergoes no dramatic personal transformation, his brief mentorship of Vestemona and his final confrontation with Gram highlight his role as a catalyst for the protagonist’s growth and a direct threat to the crew of the Aurora.