When Okajima Rokuro visits Southeast Asia carrying a top secret disk, he is kidnapped by pirates riding in the torpedo boat, “Black Lagoon”. Although he thought he would be rescued soon, the company actually abandons him, and sends mercenaries to retrieve the secret disk. He narrowly escapes with his life, but has nowhere to go. He gives up his name and past, and resolves to live as a member of the Black Lagoon...