Renge, who was visiting her grandmother's village, informs Houtaro and the others that a yokai has appeared and she wants them to come immediately. In that village, a man named Starshine Hoshino, who calls himself a specialist in exterminating yokai, appears, and his apprentice is Kajiki!?

Houtaro and Rinne arrive in the village and immediately discover the yokai! Houtaro transforms into Gotchard...!

The village chief is found in a grisly state, and the villagers assume it is the work of Starshine Hoshino and make a big fuss. They lock Hoshino and his apprentice Kajiki in a warehouse.

Kajiki would never attack anyone. As Houtaro and the others begin their search for the real culprit, a new Malgam appears. Houtarou transforms into Gotchard, but he feels something strange about the Malgam's behavior. What is this discomfort? And what is the truth behind the incident...!?

Houtaro and his team receive information that the 102nd Chemy has unexpectedly appeared. Houtaro, Supana, and Sabimaru begin a search based on this information, and arrive at a certain research institute where Sabi's brother, Ken'ichi, works.

A new Malgam appears at the institute. Is the 102nd Chemy real after all? And behind it all is the resurrected Geryon!? Houtarou and Supana transform into Riders...!

Mami, the director of Kongo Laboratory, begs Houtaro and the others to protect the laboratory from Geryon. Protect it from Geryon? What is the relationship between Mami and Geryon...?

Houtaro, suspicious of the Chemy's behavior, asks Sabimaru if it was really Kenichi who created the Chemy. For a moment, Sabimaru is perplexed, but then he reveals the truth behind the Tsuruhara brothers and Chemies. What is that unexpected truth!?