Gamera vs. Barugon

Six months after the previous events, a meteor collides with the Z Plan rocket, freeing Gamera. Gamera then returns to Earth and makes a direct assault on the Kurobe Dam in Japan.

Ichiro, a World War II veteran, dispatches Kawajiri, Onodera, and Keisuke to the island of New Guinea to locate and retrieve an opal he once hid in a cave. Locals warn them of danger, but the trio presses on; Kawajiri is fatally stung by a scorpion during the expedition.

Onodera betrays Keisuke and nearly kills him during the expedition. Keisuke is rescued by locals, and he tells Karen about the opal they found.

Keisuke entrusts Karen with the truth about the so-called opal; Karen reveals that the gem is actually an egg. She convinces Keisuke to take her to Japan to retrieve whatever hatches from it.

Onodera leaves the opal exposed to infrared light during the voyage, triggering its heat-based incubation. The heat reveals that the opal is an egg, and Barugon hatches into a massive lizard. The group continues toward Japan, unaware of the danger.

Upon arriving in Kobe Harbor, the ship is destroyed. Ichiro later finds Onodera, who confesses that Keisuke and Kawajiri died in the jungle, deepening the mystery. Barugon surfaces and begins its assault in Japanese waters.

Barugon’s rainbow ray traps Gamera in place, prompting a desperate battle in Osaka. The two colossal creatures clash as the defense forces scramble to respond. The encounter dramatizes the immediate threat to the city.

Keisuke and Karen capture Onodera and tie him up, then propose using a giant diamond to lure Barugon into a lake where it could drown. The defense ministry becomes involved as plans shift toward the diamond strategy. The plan hinges on radiation from the diamond to attract or trap Barugon.

A second attempt irradiates the diamond, but the plan falls short due to insufficient radiation. Onodera interferes and steals the gem, complicating the defense's options. Barugon then devours both Onodera and the diamond.

With the key insight that mirrors are unaffected by Barugon's rainbow beam, the military deploys a giant mirror to reflect its own attack back at Barugon. The creature is wounded as it realizes its error and stops firing the rainbow. Gamera seizes the moment and prepares to strike.

Gamera thaws and joins the battle, ultimately drowning Barugon in Lake Biwa before flying away. The city of Japan breathes a sigh of relief as the danger subsides. Keisuke watches the horizon, filled with mixed emotions.

Keisuke mourns the carnage caused by greed and loss, feeling alone after the battles. Karen reaches out and tells him he is not alone, offering companionship and support as they face the future. The act closes the journey and hints at a fragile partnership.