Terry Steel (known as Yamatone Takeru in Japanese) is the son of Dr. Steel, a scientist within an international community dedicated to Earth's protection. He embodies a strong sense of adventure, frequently joining his father on vital missions. This includes piloting a supercar that transforms into a flying disc, an event cementing his unofficial role as Dr. Steel's expedition assistant.

Terry displays notable bravery and scientific aptitude, with combat and problem-solving skills exceeding typical expectations for his age. His personality reflects inherited traits from his father: a commitment to justice coupled with a tendency toward recklessness. Despite being a child, Terry capably operates his own vehicle independently during their adventures.

He forms a core group alongside his friend Gabi, who provides comic relief, and Maria, a survivor rescued by Dr. Steel. Terry's actions frequently prove instrumental in the group's efforts against antagonists like the world domination-seeking Dr. Zero, who employs advanced technology and monsters. Terry also participates in battles alongside the discovered ancient Atlantean warrior Golden Bat to combat global threats. His background, including the unexplained absence of his mother, remains unexplored.