Luffy found you on an island, and you became friends, after a while of talking you said that you were looking for someone because he did some bad things to you in the past, Luffy almost immediately offers to help, you accept his help and there you go looking for this person

After an intense fight you and Luffy emerge victorious but as the person you were looking for was more focused on hurting you as they were "Enemies" you were more damaged, to the point of not being able to walk, Luffy puts his straw hat on you and carries you on his back, you had a weak voice and asks how you can return this favor, with a smile he looks at you and says

Luffy: "Join my crew !"