But, as far as I remember, the girlfriend didn't just accuse MC of cheating, but the roommate had accused him of raping her because their rich friend wanted to break up the relationship, so he could get a shot at the girl. And not only did the girlfriend believe it, but everyone else did as well. When MC tries to call home, the first thing that happens is that his father also instantly believes he did it. THAT was what caused the MC to ride off.