Michiru Disappears Under the Lake. A researcher discovers a horn made of an unknown metal alloy in the mountains of central Japan. A team of scientists goes to the scene during the investigation and is kidnapped by an army of demons who capture the scholars for their shady purposes. Mikiru rushes into reconnaissance, as the boys of the Getta team are busy elsewhere and when they return to the base it is too late: even the girl is lost track. Ryo, Hayato and Musahi leave aboard their shuttles and retrace their companion's route. Meanwhile, the girl ends up in the hands of the enemy who uses her to blackmail the scientists into making a powerful chemical reagent to destroy the Robot Thrower. The boys clash with the monster on duty while the scholars manage to free themselves from the clutches of the enemy, managing to save Mikiru and destroy the base, while Getta Robot eliminates the terrible mechanical monster.