A typical Japanese businessman named Rock, known as Okajima Rokuro, gets swept into the world of piracy and transportation with the 'Lagoon Company.' Alongside Dutch, Revy, and Benny, he navigates the waters of Asia on the modified vessel 'Black Lagoon.' Operating from the lawless Roanapur, a city teetering on the edge of war and ruled by international criminals, they encounter formidable figures like Balalaika from Russia and Chang from Hong Kong. As Rock prepares to return to Japan with Revy, tensions rise in Roanapur. The narrative delves into the past camaraderie of soldiers in a desert land, exploring the intimate reunion between a captain and her former subordinate.