The city of Tokyo is split between two mafia groups: The Dragon Head and The King Caesar organization. Due to a certain incident, the protagonist JJ, a well-known professional assassin, is framed and thus abandons his title, going into hiding — but more problems come his way.

It was just like any other day during lunch until today when suddenly the bishounen from my class gave me tiger-print panties!!?!

Lock n' load with the worst soldiers of fortune ever to hit the high seas of Southeast Asia! Aboard their World War II era torpedo boat, the Black Lagoon, Dutch the Boss, Benny the Mechanic, Revy Two Hand, and Rock, the salaryman from Japan, deliver anything, anywhere. In the dangerous underworld of the Russian Mafia, Chinese Triads, Colombian drug cartels, crazed assassins, and ruthless mercenaries, it's hard to know who to trust. But if you've got a delivery to make, and you don't mind a little property damage along the way, you can count on the crew of the Black Lagoon.