It's a sunny day on Christmas Island. Sonic the Hedgehog is taking a run around the island. When he stops to rest, he finds a video tape on the beach titled "Rising Tides Crashing Skies". He takes it home and watches it, and learns about the Crystal Gems, and, deciding they're a threat to the world, runs to Beach City to confront them.

Upon arrival, he finds the Beach House empty, and proceeds to wreck it, believing it to contain secret weapons and evil plans. A half hour later, the Gems and Steven arrive home to find the Beach House in ruins, and Sonic calls out to them. The Gems go on the offensive, and Sonic manages to defeat them all with his speed powers.

Sonic then proceeds to mock the Gems when Steven comes walking in. Sonic says "too easy" before running at Steven, knocking him over. Steven summons his shield as Sonic begins running at him again. Sonic begins kicking at the shield repeatedly before knocking Steven over again. He then pulls out his sword Caliburn and prepares to finish Steven with it when a bruised and burnt Eggman washes ashore.

Eggman wakes up and warns Sonic, Steven, and the Gems of something big coming. He then passes out again as a row of spines comes into view. Then, this row of spines stops halfway, and a gigantic 400-foot tall dragon-like creature emerges from the water and roars. The Gems recognize the creature from Japanese legends of a creature called "Gojira". The Gems realize that the creature is too big for their fusion Alexandrite to take on, so they propose fusing with Sonic and Eggman, and Sonic calls in his friends Tails, Knuckles, Amy, Big, Cream, Espio, Charmy, Vector, Shadow, and Rouge.

At the same time, Steven calls in his friends Peridot, Lapis Lazuli, Lars, Sadie, Mr. Fryman, Ronaldo, Peedee, Mr. Smiley, Jenny, Kiki, Kofi, Nanefua, Buck, Sour Cream, Greg, and Connie. With everybody there, they all get together and form a gigantic 300-foot tall fusion with traits of all the fusees present on it. The fusion then proceeds to battle Gojira, with neither combatant able to best the other. Eventually, Gojira leaves the area, and the fusion separates, and everybody goes their separate ways.