Black Lagoon (2006), directed by Sunao Katabuchi and based on the manga by Rei Hiroe, follows a group of mercenaries operating in Southeast Asia. The series centers on criminal operations, hostage situations and conflicts between various factions.

Från IMDB:
A Japanese businessman, captured by modern-day pirates, is written off and left for dead by his company. Tired of the corporate life, he opts to stick with the mercenaries that kidnapped him, becoming part of their gang.