Two siblings are running away from demons which attacked their village. Just when they are cornered, a mysterious female fighter appears and slays the demons. This female fighter turns out to be a Slayer, a demon that fights other demons and is part of a village of Slayers.
After Nami steals the Going Merry, Roronoa Zoro, Usopp, and later Monkey D. Luffy and Sanji (along with Johnny and Yosaku) set after her and wind up in Cocoyasi Village, Nami's hometown ruled by the tyrannical fishman Arlong. It is here that Nami's past and true motives come to light.