"Gear Fighter Dendoh" is a 38-episode mecha anime series that aired from 2000 to 2001. The story is set in a near-future Earth where humanity faces an existential threat from the alien race known as the Veln. The Veln, seeking to conquer Earth, deploy powerful biomechanical weapons called Gears to carry out their invasion. In response, Earth's defense forces develop their own advanced mecha, the Gear Fighter Dendoh, to combat the alien threat.

The protagonist, Yuuta Tomonaga, is a young boy who becomes the chosen pilot of Dendoh after his father, Dr. Tomonaga, sacrifices himself to activate the machine during a Veln attack. Yuuta is joined by his classmate and co-pilot, Kira Daidohji, who shares the responsibility of operating Dendoh. The mecha itself is unique in that it requires two pilots to function effectively, with Yuuta controlling the upper body and Kira managing the lower body. This dual-pilot system becomes a central theme, emphasizing teamwork and synchronization.

As the series progresses, Yuuta and Kira face increasingly formidable Veln Gears, each with unique abilities and strategies. The Veln are led by General Zeheart, a ruthless commander determined to subjugate Earth. Alongside Zeheart is his subordinate, Lady Zera, who harbors her own motivations and complexities. The conflict escalates as the Veln uncover Earth's secrets, including the origins of Dendoh and its connection to ancient alien technology.

The narrative explores themes of sacrifice, resilience, and the human spirit in the face of overwhelming odds. Yuuta and Kira's relationship evolves from initial friction to a strong partnership, reflecting their growth as individuals and as a team. Supporting characters, such as Yuuta's mother and members of Earth's defense forces, contribute to the broader struggle against the Veln, adding depth to the story.

The series balances episodic battles with an overarching plot, culminating in a final confrontation that determines the fate of Earth. The resolution ties together the personal journeys of the characters with the larger conflict, providing a satisfying conclusion to the narrative. "Gear Fighter Dendoh" stands as a classic mecha series that combines action, character development, and a compelling story of humanity's fight for survival.