While mining a train tunnel between Tokyo & Osaka, a construction crew unearths a strange object from within a huge underground cavern. Unable to identify the object, Jun and Yuriko venture into the tunnel to further investigate. In the meantime, Ippei and a reporter, with the help of a young boy named Liro, discover that the object is the egg of the giant bird called Litra. According to ancient legend, when Litra's egg is found, the giant monster Gomess will appear to destroy the Earth and consequently, Litra will rise up to defend against it.

Amagi Mountain (also known as Saru-yama or Monkey Mountain due to its indigenous monkey population) is discovered to be the home of a 50 meter tall giant monkey, after the animal had ingested green leaf walnuts laced with Helipron G from a nearby research facility (Helipron G, a hormone nutrient developed during World War II for the purpose of strengthening soldiers in battle is found to trigger rapid growth in monkeys following excessive consumption).

After being trampled beneath the maddening rush of a crowded Tokyo train station, Yuriko discovers crowds of people volunteering to participate in a new experiment called the 1/8 Project. When Yuriko enquires into the nature of the project, she is accidently reduced to 1/8 her normal size.