ONE PIECE MANGA VOL 9 by EIICHIRO ODA

Luffy and crew must contend with “Saw-Tooth” Arlong and his nasty Fish-Man pirates, who specialize in using mafia tactics to squeeze the lifeblood from innocent villagers. Needless to say, it comes as a big surprise to everyone that pirate-hating Nami is actually a member of Arlong’s crew!