This is an idea I just sort of came up with after watching one of the episodes, and thought to myself: why not? If this is similar to any other fanfictions, I apologise, but those similarities are purely coincidental.
Enjoy?
Steven Universe: Anticrystal
On March 30th, 2017, the Earth was demolished by a secret force known by many names across the world. The most common was "The Cluster." This event was a signal for the invading forces of Homeworld, known as the Invaders, to colonize the planet and take it as their own. Billions were killed, leaving only a few million to survive across the world, spread out from everyone. Few even know that anyone else is still alive.
In the coastal area of Beach City, Delmarva, the surviving residents have formed a refugee group that must hide from the invading forces. These residents are led by Gregory DeMayo, and his adopted daughter. They are caught in the crossfires of an ongoing war that has lasted centuries between the Invaders and a rebellious force. The people of Beach City have been cautioned to avoid both parties, as involving themselves in either will result in certain death.
The Rebels call themselves the Crystal Blades. They are a group of 5 Homeworld Gems who have rebelled against their government, The M.I.D.A.H. They have made efforts to thwart them for years. To take down their tyrannical leader and claim it as their own. And to start this plan by taking back a world that has already been lost. Even though they try desperately to win against the Invaders, the Crystal Blades have begun to lose the world they hope to take back. And The M.I.D.A.H. has taken great strides in the way of ensuring the rebels do not succeed.