Yoshitaka was no fool—he had simply misjudged an earlier decision but stuck with it, and hence, the mistake had snowballed from there.
That was also precisely why he wasn't concerned when his daughter had voiced her suspicions, even arguing as if in a knee-jerk reflex.
But now, with Kathleen explaining the whole situation, he truly came to his senses and realized how big a blunder he had just made!
Her description of what would have been alone left Yoshitaka sweating buckets, as Kathleeen wasn't