Hi Jimmy - I love how you've developed this piece. There's some wonderful strong writing and great character depiction which pulled me to the end.
I do wonder if what it is lacking is an element of change that gives short stories that complete feeling, and this is why most people have assumed it is a first chapter.
We know Al has been Scarlet before, and perhaps dark things happened in that persona. So when Al is overcome by loneliness and becomes Scarlet it doesn't feel like he's changing, just putting on a temporary skin. So tomorrow he will still be shy lonely Al, but perhaps with a dark stain on his soul from whatever he did while Scarlet. There's been no change. This is sad and leaves me slightly dissatisfied with the ending.
I'll admit I'm a sucker for upbeat endings and that may not be what you want here, but I wonder if the story needs a slightly different tilt. Al has dabbled in different genders before with bad outcomes, but now driven to the edge by his loneliness has finally embraced what he wants to be, made the change and come out on top - the caterpillar to butterfly transformation. That might give the story its transformative arc and the ending a more rounded feeling? It also might help address Jon's 'twinge of dismay'.
After the end of the story, I'd like to be able to imagine Al going to the shop the next day, maybe back in his usual day clothes, but still having that new confidence and it's Julio who is the tongue tied one.
Your story and writing is powerful and has had my grey matter whirring all morning.