Miki Saegusa of the United Nations Godzilla Countermeasures Center (UNGCC) travels to Birth Island to check on Godzilla and his adopted child Godzilla Junior, but finds the entire island destroyed. Godzilla appears in Hong Kong, covered in glowing lava-like rashes, and goes on a rampage. The Japan Self Defense Forces (JSDF) hires college student Kenkichi Yamane, the grandson of Dr. Kyohei Yamane, to work at the center in an attempt to unravel the mystery of Godzilla's condition. Yamane suspects that Godzilla's heart, which acts as a nuclear reactor, is undergoing a nuclear meltdown as a result of Godzilla absorbing the energy released from a uranium deposit on Birth Island that had been triggered by a volcanic eruption. Yamane theorizes that when Godzilla's temperature reaches 1,200 °C, he will explode with a force approximately "1,000 times greater than all nuclear weapons put together, a burst of power unseen since time began," which will be hot enough to ignite Earth's atmosphere and reduce the planet's surface to ash.