An orphan with a dream to make the map of the world, Nami was an orphan and found by Bellemere (a former marine who adopted her with her sister Nojiko). As a child, Nami fascinated to draw maps and navigation charts and had a dream to map the world. Bellemere wasn’t economically strong enough to support her with the navigation books as they can hardly manage for their bare necessities. But fate wasn’t in favor with them; an infamous Fishman Pirate Arlong took over the Commi Island and came upon Cocoyashi (Nami hometown) and imposed a tax on them in order to live. Bellemere was unable to pay the fees for all the three (Nami, Nojiko and her), so she decided to pay the fee for those two. Since Bellemere could not pay the fees, she was used as a demonstration for what will happen if they refused to give the tax, she was brutally murdered by Arlong. Nami was then kidnapped and forced to become a cartographer for Arlong, when he notice her maps drawing. He gave her a deal, a deal of the lifetime as a crew member in his pirate crew and in the mean time she can keeps on drawing charts and maps for him and if she gave him 100,000,00 berry then she will be free and her village too. She accepted the deals for her village and started stealing money from other pirate ships and become a cat thieve. She spent eight years making maps for Arlong and stealing treasure from other pirates in order to buy her village back.
During that time many events happened, she managed to steal a map of grand line from Buggy the clown. When she was running from Buggy’s henchman, she noticed a flying bird coming straight in her way, it was Luffy (He was stuck in a bird mouth and then probably that bird dropped him). She used Luffy as bait to get out of the situation and after that when Luffy noticed that she is a navigator, he offered him to join his pirate crew. But when she knows that he is a pirate she refused as she despised pirates (because his village was captured by a pirate and a pirate killed Bellemere). So she played a game and hand over Luffy to the Buggy to gain his trust and planned to rob him later. But after that Buggy commanded Nami to blow Luffy with buggy canon but she can’t do it and fights back. Here where our Zorro entered and safe the day, they run and hide for a while as Zorro got a bit injured during the fight. Talking about our captain Luffy he was caged so he wasn’t very much helps but when he got freed they (Luffy, Zorro and Nami) charged into Buggy again. Nami played tag-tag game again and tagged with Luffy and Zorro as she feels safe with Luffy and Zorro though she wasn’t very much help. Luffy blew Buggy into the stars and then those three set sails into the grand line. Nami tagged with Luffy because Luffy lost her treasure as he intentionally dropped it at the island for the damage they cost. Second reason for her to be with them was that they were strong and they can give her a bit of protection while she steals treasure from other pirates. This is how our Monkey D Luffy got her second crew mate. Though after quite some time, she betrayed Luffy and other crew members for the sole purpose and sake of her village. She collected the amount Arlong demanded to free her village but Arlong betrayed Nami by sending marines in her house to collect the amount she stole. After that Luffy and other crew member go to the Arlong to take her navigator back and safe the day. After that Nami was officially became a navigator in the straw hat pirate.