In episode 31, Usopp was saved by Mijiko who was Nami’s sister. Nami is the cadre of Arlong Pirates. In fact, she didn’t like to be the cadre of it, but she has to be to save her village. Arlong has ever promise her that if she gives 1 billion beri to him, her village will be liberated.
  Zoro was caught by Arlong Pirates in episode 31. In One Piece Episode 32, Nami says to zoro that treating them well is just for the money. At this time, Arlong chips in. He says that Money is everything for Nami, even more important than her parents’ death. Zoro takes note of Nami’s expression when Arlong said these words. Zoro jumps into the pool and Nami saves him, which proves that Nami is a kind girl.