Masaru Kodaka, often referred to by the nickname Kodama, is the third child selected to pilot the giant robot Zearth in the series. He is the son of a wealthy real estate developer who runs a civilian contracting company. Kodama is a relatively quiet boy who keeps to himself, but his upbringing under his father has deeply warped his sense of ethics and morality. He believes that he and his father are chosen, superior beings, and that the suffering of others is an unavoidable consequence of the success of the powerful. This worldview leads him to take pleasure in cruelty; before his battle, he is shown burning a crab to death for amusement and later shooting stray cats with a pellet gun. He idolizes his father above all else, viewing him as infallible, and even wears a pair of glasses similar to those worn by the previous pilot, Kokopelli, in an attempt to appear smarter like his father. Kodama’s two older brothers resent their father and seek different paths, but Kodama remains devoted to him.

As the pilot of Zearth, Kodama shows no concern for collateral damage. During his fight against the enemy robot Cancer, he makes no attempt to avoid civilian casualties and instead marvels at the destruction he causes, resulting in an estimated fifty thousand deaths. His sense of wonder is shattered when his robot crashes down onto his father’s car, killing his father instantly. Stunned for a moment, Kodama gathers himself and uses his understanding of construction, gained from his father’s business, to land a decisive blow against Cancer. He defeats the enemy but dies immediately afterward, unceremoniously. His death is the first to explicitly reveal the truth of Zearth’s life-force cost to the remaining children, alerting them that each victory comes at the price of the pilot’s life.

Kodama’s role in the story is brief but significant: he serves as the second casualty, demonstrating the brutal reality of the children’s contract and the moral depravity that can arise from unchecked power and paternal influence. His relationship with his father is central to his character, defining his arrogance and lack of empathy. His development is minimal due to his early death, but his actions highlight the series’ themes of consequence and the corruption of innocence. His notable abilities include a practical knowledge of construction and a ruthless willingness to use Zearth’s power without restraint.