Let's break down the phrase:
The wife might still say no. She might still roll her eyes. But she would not feel betrayed. tsuma ni damatte sokubaikai ni ikun ja nakatta
In any healthy marriage, transparency is the currency of intimacy. By sneaking off to the convention, the husband has committed two subtle but significant betrayals. Let's break down the phrase: The wife might still say no
Here's a possible article based on this sentence: at his core
The man who says “tsuma ni damatte sokubaikai ni ikun ja nakatta” is, at his core, realizing: I prioritized my immediate desire for a few hours of shopping over my spouse’s right to know what happens in our shared life.