Marco was on the roof of his suburban house, Star's part of the house was gone. She was gone. His hope for their future was gone. One thing that wasn't gone was the change in Marco, his confidence, his sense of self worth, his love and respect for Star.
Star was the first good thing to really happen in his 14 years alive. His parents never really cared enough about him to notice he was depressed. He always looked at Jackie from a far, and he was just socially awkward in general. All of sudden Marco realized tears were rolling down his face. Star was his happiness. He should have told him how important she was to him. He should have told her the truth. There had to be a way to get to her. He thought she wouldn't have just left because of him, come to think of it he did hear a woman's voice upstairs while the party was going on. Something was not right. He had to get to her. He had to, at the very least, talk to her, see her, feel her.
He remembered Star hid a pair of dimensional scissors in his closet. He hopped down from the roof and ran to his closet. He searched and searched, but nothing. He thought, 'if I was Star where would I put these?' He then realized it wasn't in the closet it was in her drawer in the bathroom. It was her junk drawer basically. Lo and behold there they were.
'Now how do I work these things again?' Marco said aloud. He opened them and they instantly opened a portal. He was taken somewhere very warm and when he could finally see the world he was in after being blinded by the portal. He realized he was in the underworld where Tom resided. 'Great' Marco thought. But wait Tom might have the tools or , well, something anything to get to Mewni. Marco was willing to put his life on the line, make any promises he needed to make anything to get to Star...