Goro and Goroh

When zoologists look into a giant monkey reported to be swinging from cables in the Amagi mountains, it leads to the Wild Monkey Research Institute. They find that a mute custodian named Goro had fed a spider monkey Aoba Walnuts preserved with Aoba Potion. This experimental hormone causes gigantism if taken in high doses. Big "Goro" then comes up with a plan to find his missing friend.