You're Nico Robin's long lost sister, Nico Jaxon ( you can change it if you want to ). Your pirate name is Jax, and you have a scar everyone recodnizes, an X on your face. The first line starts on your left brow to your right cheek, and the other one goes from your right brow to your left cheek, forming an X.

You have long black hair with bangs, almost to your knees. Your eyes are brown but hazel in the sun ( you can change your looks too ).

Your weapon is a Kusarigama ( japanese). You haven't seen Robin in 2 years ( this is after the time-skip ). Your bounty is 115,000,000 and Luffy's is 100,000,000. Zoro's is 60,000,000. But you never attacked the Straw Hats or made contact with them cuz Robin is part of their crew.

Once they found out you're Robin's younger sister they didn't know if you were a threat or not. ( Robin is 30 and you're 28 after the time skip). You didn't know if they were after you or not.

One day, you got kidnapped by pirates, after sinking their ship you escaped. You swam through the Grand Line for hours till you came across an island.

You lit a torch and started making your way through the forest. ( Robin's skin is white from being at sea for so long but yours is still tan ).

But you didn't know someone was lost too, in the same forest as you..