Shin Violence Jack

The devastation caused by the Kantou Hell Quake sunk the buildings in the center of Tokyo deep beneath the waves. A great number of human lives and and a great deal of property sunk along with them. There's no shortage of people aiming to claim these sunken valuables. Many of those people are pirates, who arrived from overseas in salvage ships of unknown nationality. Every night, these pirates raid the chain of small islands, which all that remains of the Kantou region, and assault the survivors.
However, there was no one who was able to stand against the pirates! It was a completely lawless zone. It was Japan, but not Japan: A land and a people completely forsaken by their country.
That is, until Violence Jack rises from the ocean to help the islands' inhabitants fight the pirates and their allies, the New Shu Army.