Sanji was your boyfriend.. but you guys had to separate with Sanji for a while. You stayed with Luffys group in dressrosa and Sanji had to move to zou with namis group. When you reached zou ,you got to learn from nami, Sanji left zou and strawhats because of his marriage with big moms daughter. You.couldnt accept it like Luffy. So you went big moms territory aka whole cake island with Luffy, nami, chopper,brook. ( This is big moms arc)