Doesn't Jessica have a Feminization/Sissification mirror?
Yes, but the Sissy aspect of the mirror is a means rather than an end. Part of why I like "outfit play" so much in ToT is that being a proud member of the Fire Dojo a major fixture of the MC's personality.
Stripping him of his coat (or in general) is humiliating (eg. Crow). Having him wear something else is completely degrading (eg. Jessica, Yvonne). Breaking him enough to /willingly/ wear something else long-term (eg. Puppy Gear, unreleased Cobra) represents basically complete (though perhaps not totally irrecoverable~) subjugation which is why it's reserved for major scenes/mind-breaks/etc.
In this case, wearing nothing but blush and pretty pink panties isn't about making you girly, it's about creating contrast between the warrior/hero that was and the submissive slave-boy that Mistress (Jessica in this case) made you. And although the MC is hardly a chad, there is a natural masculinity of a determined monk lad, and I think inverting that adds an extra layer of thrill/contrast that eg. the Gimp or Puppy outfit might not.
Regarding my comments recalled by
Ethan (temporarely) (which remain generally accurate): I'll add that I actually tend to like the (usually early) sections of sissy games where the MC is shyly exploring panties or chastity or whatever at the behest of their Mistress. At these points the real "play" is more in the realm of servitude, seduction, corruption, and humiliation than TG/TF/Feminization/etc. Then I bail once the focus shifts to the latter as those are big turn-offs for me.
Similarly I could write a whole essay on how I actually only like puppy stuff within a particular context/execution and generally find it annoying otherwise, but I'm sure you'd all prefer I spent that time on our upcoming Demonesses instead.
Anyway, I hope the Jessica dress-up (panties, pantyhose, etc.) was enjoyable even to not-sissy-fans (eg. me), while hopefully scratching the itch a bit for actual sissy fans, even if it doesn't go in the thematic direction they're probably used to. The mirror meanwhile lets you double down on that if you're into it, while providing a little extra depth just by being an option if you're not (eg. picking Gimp out of 5 options feels like more of a choice than of 2 or 3).