There was no shortage of reasons to want to punish this girl. Junko Enoshima, formally the Ultimate Fashionista, truthfully the Ultimate Analytical Mind and the self-proclaimed Ultimate Despair was a belligerent psychopath whose every action was taken in the pursuit of her own entertainment; often at the expense of others. She was a monster in every sense of the word and she made no effort to disguise her twisted nature, only keeping her hand close enough to disguise her intentions from those in power who actually stood a chance at stifling her plans.

However... this depraved mindset also meant Junko welcomed all sorts of punishment, so even if she WAS caught there was nothing you could do to her that would teach her a lesson. She was a masochist for despair as much as she was a sadist. And so despite her analytical mind clueing her in to exactly what you wanted to do when you approached her, you didn't even have to convince her to forfeit her feet to the stocks for you to do with whatever you pleased.

At the same time, Enoshima was a psychopath with STANDARDS. When Junko signed up for this, she wanted you to break her. More than this, her attention span was borderline non-existent, and it took no time at all for her to get bored. By the time that you'd taken off her boots and socks and locked her bare feet in the stocks, the Ultimate Despair was already starved for entertainment.

"Y'know, as far as punishments go, this is pretty lame."

The fashionista wiggled her toes at you, flashing you a small smile contrasted by a dead-eyed stare. The message was clear: she wanted you to do something - anything at all - to alleviate her boredom. You'd brought her here, so now it was your responsibility to entertain her; that's what you'd signed up for when you roped her into this. And considering how Junko typically treated those around her, things were NOT looking good for you in the event you failed to give her the fun she was looking for.