A young boy named Taro develops a curious preoccupation with his pet turtle named Gameron, to whom he constantly encourages to grow. After getting into trouble for bringing his turtle to school and neglecting his studies, Taro winds up in the company of two bumbling gangsters as they flee from the authorities. While hiding out in the sewer, Taro is delighted to find that his turtle has suddenly grown to 99 cm in length. The sight of the giant turtle, however, frightens the gangsters into the welcoming arms of the police. Assuming that Taro had been kidnapped by the two thieves, the authorities return to collect the boy, who is nowhere to be found.

Yuriko and Ippei are passangers on the inaugural voyage of the Inazuma; a futuristic bullet train leaving New Tokyo Station for North Kyushu. Mistaking it for Yuriko's case, Ippei accidently brings along the high-pressure container which houses Dr. Aikawa's artifical lifeforrn, M1.

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).

When Yuriko investigates increased volcanic activity in the Mt. Fuji area, she learns the story of a modern-day Tarzan named Takeru, who is rumored to live in the region's dense woods since becoming lost within them 15 years ago. Meanwhile underground volcanic energy creates boiling temperatures in a lake at the foot of the mountain and a huge boulder erupts from the waters. Because the rock obstructs a main travel route, it is blasted apart with dynamite and the pieces are transported back into the forest. At one night, the pieces collect around a strange luminescent rock, creating an enormous rock monster called Gorgos that lives and breathes like an animal.

A strange occurrence at the zoo has caused the animals to disappear and has left the zoo keeper near death. Gasping his last breath, the dying man murmurs, "I saw a bird".

While aboard a cruise ship for the evening, Yuriko finds a child's doll, which suddenly speaks to her. The voice introduces itself as Zemi, an alien from the Planet Ruparts, and warns of an invasion from outer space. Shocked, Yuriko throws the doll overboard, but Jun and Ippei take little heed to her story.

A strange disturbance in Tokyo upturns the ground and shakes the buildings as if something huge is moving beneath the foundations of the city. In the canal of the Imperial Palace, a large tentacle-like vine called Juran appears, frightening passersby. Following this incident, Jun, Ippei and Yuriko witness an underground attack on humans, as the vines try to suck blood from their victims. Dr. Ichinotani suspects that a giant plant has taken root beneath Tokyo.

Jun, Yuriko, lppei and Dr. Ichinotani visit a laboratory near Mount Isa to learn more about the experiments of a researcher named Kimura. Kimura has developed a special nutrient called Honey Zelion, which he has fed to colonies of bees. Following an incident of vandalism at the greenhouse where the bees are stored, a giant mole called Mongula appears, terrorizing the farmland community.

Jun, Ippei and Yuriko investigate a hillside accident involving a truck that was transporting a uranium capsule. After rescuing the drivers, they learn that the monster Pagos had surfaced from underground, following the appearance of a mysterious rainbow, and caused the accident.

Following the destruction of a fishing vessel by a gigantic octopus, the lone survivor named Yuzo, the son of the ship's captain, is washed ashore nearby Compass Island. He is rescued and cared for by the beautiful native girl, Anita and the two begin to develop affections for one another.

Acting as a special correspondent for the Daily News, Jun travels to Japan's base at the South Pole. Once there, he learns about the mysterious disappearance of staff member Nomura three years ago, an incident that is made more intriguing by a passage in Nomura's journal which refers to the unknown entity, "Peguila". Yoko Kuhara, staff physician and Nomura's fiance, is also stationed at the base and remains optimistic that they will find the missing Nomura. Soon, strange disturbances begin to take place, as well as a dramatic drop in the region's temperature.

A mysterious lifeform adheres to the rocketship Saturn I on its return trip following the exploration of Saturn. The alien creature absorbs the rocket's energy, causing it to crash into the sea upon re-entry into Earth's atmosphere.

While driving home one evening, Jun and Yuriko come upon a man lying unconscious in the road. They help him into their car and drive off. When they stop at a railroad crossing, the sound of the oncoming train startles the man awake, sending him into a fit of hysteria.

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.

When several boys discover a mysterious, lightweight meteorite, their teacher delivers the strange rock to Dr. Ichinotani in Tokyo. Under analysis, the meteorite which the children call garadama, is identified as being comprised of Tilsonite and is found to be emanating powerful radiowaves.

Residents are horrified when reports of skeletal remains and giant footprints lead them to believe that an abominable snowman may be lurking in the nearby mountains.

Jun and the others attend a perforniance by Akanuma the Magician During the act, a young girl named Lily is enclosed inside a box and her ghostly spirit appears in the air, separated from her body. At the conclusion, her body and spirit are rejoined and she emerges from the box, generating applause from the audience.

When Jun and Yuriko sight a UFO, it is discovered to be a lost space capsule that has returned to Earth after a trip to Mars. The unmanned capsule is found to contain two small gold spheres. Before the objects can be scientifically identified, however, they are stolen by a thief who mistakes them for real gold.

Returning home from a party one night, Jun and company become lost in the outskirts of Tokyo. When Ippei and Takehara accidently stumble into a marsh, the group seeks refuge in a nearby Western-style mansion to help keep the two men warm.

At a Tokyo airport, a sudden, mysterious cold wave causes an aircraft to crash and grounds the other planes. A strange black cloud descends on Tokyo and from within it, emerges the monster Peguila.

One day at a construction site, a group of children were finding valuables in the dirt when a man on a bulldozer ran over their bikes. When the children went to recover them, one of them named Kaneo Kaneda (in Japanese, kane means money) found a small object that had a jingle sound much like money in it.

Under the cover of night, a mysterious man steals the Tilsonite rock from Tokyo's Astrophysics Research Institute. When a group of meteors is detected approaching the Earth, Jun and the others fear that an invasion from outer space is once again imminent.

A ring of smugglers, including a mysterious woman named Aleen, steal a rare statue and kidnap a young girl named Tami in the process.

Joe Aikawa, better known as Dynamite Joe, takes Japan by storm as he rises through a series of decisive victories to become the country's new boxing champion. Prior to the match for the world championship title however, Joe mysteriously disappears from the sports world, creating controversy towards his promoter.

Returning from a pilot's conference in Hong Kong, Jun and Ippei's flight aboard a supersonic passenger jet is suddenly interrupted by a strange pocket of turbulence.