After King Ghidorah was killed for the second time in "Island Kaiju Battle", a different King Ghidorah takes his place. Mothra's son, Rainbow Mothra Leo, is the only one who knew this. At a mystical cavern on the island of kaiju where Mothra and her son were sleeping, Rainbow Mothra Leo senses danger as he wakes up and rushes out. In the cold of the night, Leo looks around. He finds nothing, but then hears a bell-like cry. It was the newer King Ghidorah, rising to take over the Earth. Leo worries, and circles around. When he sees Ghidrah flying high up, he bravely follows and catches up to the three-headed kaiju. The two begin clashing and the battle begins to move to land. 2004 Godzilla sees the two, and knows that Rainbow Mothra Leo can't win against this
Ghidrah all by himself. The King of Monsters heads to Mothra's mystical cavern and alerts her that Leo is in danger, while Rainbow Mothra Leo grabs on to one of King Ghidorah's necks and shoots a Mega Breast Cannon from his chest, almost cutting the head off. Ghidrah screams and flings Leo off. Mothra and 2004 Godzilla come out of the cavern and head for Leo and King Ghidorah's battle. When they arrive, one of Ghidrah's heads is looking at and biting Rainbow Mothra Leo, while the other two heads are angrily staring at Mothra and 2004 Godzilla. Those heads each zap 2004 Godzilla and Mothra, who are only just pushed back. Rainbow Mothra Leo is shooting Mega Breast Cannons and Rainbow Busters at King Ghidorah, but he seems to be barely affected! Mothra shoots a triple prismatic beam and 2004 Godzilla shoots an Atomic Ray. Ghidrah temporarily pushes Leo out of the way, then picks up Mothra and 2004 Godzilla with his heads and throws them far away. Rainbow Mothra Leo gets up and approaches the three-headed kaiju. King Ghidorah frowns at him with barbaric anger, then zaps him with a gravity beam. Leo tries to use the reflective green powder from his wings, but was too slow and got very hurt. Mothra and 2004 Godzilla got back up and headed back to the battle. Leo was on the ground, almost dead, and King Ghidorah was about to kill him, but Mothra and 2004 Godzilla shot their beams and finally killed the horrible dragon. Mothra comes up to her son, and helps him get up. The two giant moths fly in to the distance while 2004 Godzilla walks away in the opposite direction, glad with the defeat of the horrible King Ghidorah.