This is the moment alot of people seem to think Marco suppressed his interest in star romantically. Think about with a simple open mind for sec,
-Up to this point the only girl who's gotten to be real close up to marco has been star, She's the only girl that has given him constant attention.
-At the same time Marco knows he likes jackie but hes not had the balls to even talk to her, more or less hes is thinking that jackie is out of his league.
-Star having given the right combinations of interactions and situations to marco has sparked a very slow interest in her in his mind. Blood moon ball happens because for onces, I think he felt that the girl that was so willing to have fun with him and that he enjoyed having fun with, was gonna go out and have fun with someone else therefor Marco got jealous and went after her. We can also compare this to BBTBC where Star uses the spying spell to see what marco is up too, She was under the same situation, ( the person she liked having fun with was out hvaing fun with someone else) so when she had the fun Marco was having her feelings caused her wand to go green and without even think about what she was doing made jackie and Marco Eat shit while falling off the skateboard.
--- When marco was told on this balcony "I dont need a hero, I need a friend" He in his mind heard " I Dont need a love interest, I just need a friend" At this points Marcos attraction to star was just a spark so with this Rain fall of a statement it made it easy to see marcos spark be suppressed by his Emotions and continued to be himself, because thats what star wanted him to be, Himself, or in other words Her friend