Part 1

The sirens, having been pushed back in recent years (mainly due to the humans complete exploitation of the shipgirls with most if not all having bad or horrible living conditions and being severely overworked), decide to build an expiramental ship-class known as the dreadnought with better weapons and ai. Sadly an operation gone wrong leads to the fleet escorting the only dreadnought built deep into enemy territory destroyed with the dreadnought itself barely surviving because of the overworked shipgirls forgetting to check if it was dead within the many floating wreckage.