Who was Erwin in love with?
Erwin was in love with a girl name Marie, which i believe has never been shown even once by Isayama. He didn’t end up with her because he chose to join the Survey Corps over her, Contrary to his friend Nile, who ended up joining the Military Police, marrying Marie and making three kids with her. Erwin gave up on a relationship with Marie so he could continue pursuing the truth and Nile changed his plans to marry her. After graduating, Erwin joined the Survey Corps, where he stopped sharing his theory with others.