Punishment of the Damned (Prototype)

The war between humanity and the Sirens rages intensely. In a desperate bid, humanity creates the so-called "shipgirls" to combat the Sirens. However, one fateful day, every human and shipgirl vanishes without a trace. The Sirens, perplexed yet jubilant, colonize Earth, only to discover abandoned buildings. Unbeknownst to them, the fate that would be fall them.

No. This isn't going to be long... maybe. This is from the Sirens POV btw.