Can I visit my sister?

I’m born 09 so im turning 17 this year but im 16 right now. My mother brought me and my younger siblings to Djibouti from Sweden in December to visit family for a short time but that has turned into months.

Now I wanna visit my older sister who’s 19 and lives alone in Sweden, same apartment our family used to live in before we came here.

Can I just book a round way ticket and have my passport (it’s a Swedish passport) and visit her or do I have to get any sort of consent letter signed from my parents?

I just thought that since I’m visiting Sweden with a Swedish passport and I am a Swedish citizen it wouldn’t be suspicious for like trafficking or something like that so they wouldn’t ask for a permission letter?