海の底から、俺は王になる

The Empire's top commander Arthur is betrayed by his wife and right-hand man, who poison him and dump him at sea. He's hauled onto pirate ship Blackwater and claimed as a husband by Elara. Written off, he kills the Whitebeard chief, unites the pirate crews, becomes king of the sea, then takes the capital, gets revenge and founds a pirate republic.