I think it's when she loses the baby, and how he incurred debts. It's partly true that Micheol threw away a promising future because of Haesoo, but it was his choice due to the circumstances. That's why teenagers shouldn't make important decisions in the heat of the moment. Micheol went from being a good person to someone who blames others for his own decisions.
I don't know what to say, I don't have money for therapy so I read yaoi.