Kaine Wakaba, a sixteen-year-old Earth Alliance military trainee fresh from a Japanese academy, lives on the space colony Alucard with his mother, the colony's administrator. His parents' separation, caused by his father Jim Austin prioritizing military duty over family, fuels Kaine's resentment. When the United Lunar Empire Giganos attacks Alucard, his mother is seemingly killed, driving Kaine to fight Giganos.

During the assault, Kaine and friends Tapp Oceano and Light Newman encounter a dying Giganos spy who gives them three activation disks. Pursued by enemy forces, they discover three prototype Metal Armors called Dragonars. Kaine uses one disk to activate Dragonar-1, becoming its permanently locked pilot via biometric security. He and his friends defend the colony, later becoming frontline pilots for the Earth Federation Military (formerly Earth Alliance) in the war against Giganos.

Kaine later learns his mother survived the Alucard attack but was captured by Giganos. They exploit her as a hostage to pressure him, aiming to cripple Earth Federation morale and strategy. His father, Jim Austin, serves as an accomplished pilot within the Earth Federation Military, their relationship remaining strained throughout the conflict.

As the war intensifies, Kaine repeatedly clashes with Giganos' elite pilot Meio Plato, the Blue Hawk. Their confrontations build until Meio is framed for treason. Kaine ultimately allies with Meio to confront the true antagonist, Dorchenov. They coordinate a tactical assault targeting a weakness in Dorchenov's machine, finishing him with a combined beam sword strike.

Following the war's resolution, Kaine continues his service as the pilot of Dragonar-1 within the Earth Federation Military.