A blue monster who can shapeshift and transform into a shadow. He attacked Joe the Haze while he was with an old lover of his named Saila in an attempt to obtain her necklace, which contained battle plans against Crisis and ended up injuring Joe in the process. Luckily, Kohtaro transformed into Kamen Rider Black RX and battled Bang-Gong. Kamen Rider Black RX got them to safety in Ridron which also tackled Bang-Gong. Unfortunately, Bang-Gong followed them and later kidnapped Saila. When Joe and Kohtaro found her in an abandoned warehouse, they were ambushed by Bang-Gong and the Chaps. Kohtaro transformed into Kamen Rider Black RX and fought him. As Bang-Gong swiped the necklace, RX became Bio Rider and followed him outside. Bio Rider took back the necklace and then called forth his Bio Blad