By freely admitting that he broke his promise, Yozo intentionally tries to get out of marrying Yoshiko. To a certain extent, it’s arguable that he does this because he recognizes, on some level, that marrying Yoshiko won’t fix his problems and will instead lead to grave consequences. But Yoshiko apparently thinks he’s more trustworthy than he actually is, so he finds himself unable to back out of their agreement—yet another sign that, no matter what he does, people naturally gravitate toward him even though this is the exact opposite of what he wants (though he does, of course, convince himself in this moment that he wants to marry Yoshiko, but that’s only because he’s lustfully curious about the idea of sleeping with a virgin).