Robin is so protective of her and is always explaining to her how the planet Earth is, Starfire is so caring especially towards Robin and enjoys Robin teaching her the ways of Earth. They start out as enemies who fought and bickered almost their entire first meeting, but then, throughout the series, they slowly fell in love. But in the end when they get together it gives you satisfaction. And when Marco leaves to be with her she's with Tom. Then Star likes Marco but she has to leave.
We start it off with just friends because Marco likes Jackie. Star and Marco's love story was a journey. I guarantee this couple will happen.someday. This ship is very in "Blood Moon Ball" (spoiler) when the blood moon was still shining on the two at the end, and in the episode with the cube, as soon as Star shouts Marco's name it says "Truth! Star Butterfly has a crush on Mmm." but you get the idea. Over the course of the series, Star's crush on Marco becomes more and more obvious and there actually have been moments where Marco seems to have some feelings for Star. Jackie and Marco are a good couple, but STAR and Marco, however. Eventually, Star and Tom break up AGAIN and the two discuss that they care about each other and get. In "Lava Lake Beach" we see that Marco DOES like Star back, but Star is back together with her X Boyfriend, Tom.
Near the beginning of season three Jackie dumps Marco because she believes that his friendship with Star is more important then being with Marco. We then learn in the end of season two that Star has a crush on Marco, and admits it to him. In the second season however, we start to see Star acting strange when Marco goes on a date with Jackie. The first season of this show started off between them not having any interests in each other at all, besides Marco had a crush, Jackie. If you had a time machine and went to the time line of when the show first started, and told Marco that this crazy foreign exchange student was going to become his friend, to his best friend, to his crush, and then to his girlfriend, I bet he wouldn't believe you.
I've been longing for them to have their first kiss and be couples ever since the show started. They are the best cartoon couples I've ever watched.