The Great Leader, overlord of Destron, arrives in Japan. When V3 and Riderman go after him, they fall into a trap. Meanwhile, Destron mutant Thorned-Starfish puts into action his plan to annihilate Tokyo. In the grip of suffocation, V3 and Riderman are saved when Tachibana Tobei comes to their aid. V3 and Riderman fight Thorned-Starfish, but when V3 turns to take on the Destron Leader, Riderman suddenly takes a stand to defend him�