We don't know that yet. In the last episode of season 2, he officially found out that Star likes him and she left before he could even reply. Before Songday, he had no idea that she liked him and thought that they were only best friends because she made it sound like a friendship is all that she wanted from him by encouraging him to go out with Jackie. So, in a way, Star made the situation worse for herself by not confessing sooner.

Marco though, ran after her as she ran upstairs to try to talk to her about it which makes me think that he doesn't have bad intentions for her feelings or their friendship (or something a little more).





It'd be a much different scenario if Star confessed to him sooner and he flirted with her on purpose knowing that she had feelings for him, but didn't feel the same way afterall and was like "lol jk" and then went out with Jackie.