Amara is a central figure in the narrative of Captain Earth, initially standing as one of its primary antagonists before his path leads to a significant shift in allegiance. He is a Designer Child, a genetically modified human created to serve as a pilot for advanced weaponry, and serves as the terrestrial avatar for the Planetary Gear known as Amarok. His physical appearance is distinct, characterized by white hair and amber eyes, though some sources also describe him with blue hair and yellow eyes, and he is occasionally referred to by the nickname Midnight. Amara is among the first of the Planetary Gears to awaken, and in the early stages of the series, he takes a leadership role among them, guiding their actions until the awakening of another figure, Setsuna.

Amara’s personality is marked by confidence, assertiveness, and a pragmatic, risk-taking nature. He is highly independent and tends to value logical decision-making over emotional considerations, often acting on instinct and a desire for novel experiences. This makes him a formidable and unpredictable opponent. However, beneath this aggressive exterior lies a complex individual whose motivations evolve over the course of the story. Initially, his primary goal is to prevent humanity from propagating the Planetary Gears, alien entities intent on assimilating Earth's resources. Yet as he learns more about the Planetary Gears' own sense of loneliness and their search for a home, he develops a deep empathy for them, identifying with their plight.

In the story, Amara functions as a direct threat to the protagonists, particularly Daichi. He possesses extraordinary physical capabilities that far surpass those of a normal human. His strength is immense, enough to bend the corner of a wrestling ring with a single knee strike, and his agility allows him to perform superhuman leaps. He is a top-tier combatant, able to defeat armed men with a single punch and hold his own against champions like Baku. Amara is also highly proficient with firearms, displaying accuracy sufficient to graze an opponent's face with a shot, and is a skilled pilot of his Machine Goodfellow mecha, capable of destroying military weaponry and posing a significant challenge to the Earth Engine Impacter.

His key relationships are fraught with tension and complexity. He shares a close and enigmatic bond with Moco, another Designer Child with whom he is often partnered. They share the same goals, and there is a notable synchronicity in their actions, yet the exact depth of their relationship remains a subject of observation. A significant connection exists between Amara and Teppei. When Teppei destroys his Ego Block and severs his ties with the Planetary Gears, Amara reacts with extreme bitterness, feeling a profound sense of betrayal that leads him to antagonize Daichi, whom he blames for the situation. This event is a key catalyst for his character development. Furthermore, a critical and darker aspect of his role involves the awakening of Setsuna, where he chases down and forcibly kisses the terrified girl, an act presented as a necessary ritual for the KTG royal lineage but depicted as a disturbing violation.

Amara’s development is central to his character arc. He begins as a seemingly straightforward antagonist, but his growing understanding of the Planetary Gears' deeper backstory and his identification with their existential loneliness lead to a moral shift. Ultimately, he becomes an integral ally to the protagonists, working alongside Daichi and the others. His journey symbolizes themes of redemption and the power of forgiveness, transforming from a force of havoc to a complex figure who fights to save the planet. This evolution is informed by his background; he is one of the Designer children created illegally by Macbeth Enterprises, and it was through an experiment by the company that he first awakened as the Kiltgang Amarok, an event that led to a devastating assault on a lunar base years before the main series begins.