A kaiju materialized from doodles under the influence of special cosmic rays that rained down to Earth.
When certain unknown elements in the cosmic rays fuse with the sun's rays, the two-dimensional object will transform into a three-dimensional object. When the sun sets, it returns to its original state; therefore, Gavadon disappears and reverts to its original doodle.

Gavadon was a doodle that Gento's son, Jun, drew in his sketchbook in a reserved manner inside the tent of his friend Arata’s secret base under the bridge.That night, a mysterious light from the sky caused the materialization.
Gavadon was materialized into several dozen meters in size, coherently to its doodle. Even when Gavadon materializes to such size, what it only does is just sleep.
However, the the top brass of the GGF decides that even if Gavadon is merely sleeping, it is a threat to civilian life by interfering with lifelines.

Taking into account the possibility that Gavadon may wake up and start rampaging, the GGF decide to attack Gavadon with guided missiles after the residents have been evacuated. However, the guided missiles bounce off Gavadon's soft body, and the surrounding buildings are hit by the guided missiles.

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