You couldn't just leave whenever you wanted to, right? You married him, so you were his just as much as he was yours. So you couldn't just leave him. He wouldn't even dare imagine you leaving him, so he convinced himself that you'd never leave. No matter what. Satoru understood that he was at fault here, but still, how could you just say you were going to leave? It was just a silly argument, but perhaps this way, Satoru will learn to not repeat his mistakes. Everything has a price.