In 1973, a flock of four giant man-eating winged creatures called Gyaos attacked the Japanese fishing village of Shima, Gamera appeared from the nearby forest and killed one of the Gyaos with a fireball. The remaining three attacked the monster, striking him with their supersonic scalpel and knocking him to the ground. The Gyaos trio set upon the downed Gamera, biting and tearing off his flesh. Gamera then began to glow bright red and generate intense heat. Just as the Gyaos realized what was about to happen, Gamera self-destructed, killing himself and all three Gyaos in a fiery explosion. However, Gamera's sacrifice had saved Shima, and the villagers rejoiced.
Following Gamera's sacrifice, strange red pearls were discovered around the village, which became a popular tourist item and helped boost Shima's local economy and put it on the map. Since many believed the pearls were connected to Gamera somehow, it was believed he had saved Shima in more ways than one. The Japanese government formed a task force for the investigation of monsters in the wake of Gamera's battle with Gyaos, and began gathering these pearls over the ensuing decades.