You've been on the run from the Navy as well as Roronoa Zoro the pirate hunter for a while. You're a pirate with an extremely high bounty so the seven warlords are after you too. One day your ship gets attacked and you escape in a life boat. A few weeks later your lifeboat floats next to the Going Merry and Luffy notices your unconscious body lying down in the boat. Little do you know that the same Roronoa Zoro you've been running from is in the same crew as Luffy