Told you I'd read this eventually.
Alright, so first up I have to say: I loved this story. I don't think "really like" cuts it here. It drew me in as strongly as any of Martin's short stories, which are among my favourites. So hopefully that gives you a gauge of how much I enjoyed this.
What made it so good? A lot of different aspects, all pulling together as one. I think a lot of the writing style you used in this piece - it was clear, it flowed beautifully, and there were a lot of strong and memorable uses of figurative language throughout. "The flame was extinguished and he was now painfully aware of his burns." I thought that line was fantastic. And "He released a breath he did not realize he had been holding", even though I feel like I might have read a similar line somewhere before in my life, just worked perfectly for that moment. I didn't find the tone weird like you said, but I think I get where you're coming from about taking it seriously. I suppose the writing style could be a bit ... light? Like it doesn't quite match the darkness of Kenji's addiction? I don't know - but in any case, I like it the way it is. Too much seriousness would leave the reader feeling very differently in the end, I think; and besides, the lucid and clean writing style depicting a dark subject kind of ties in nicely with the glittery facade of the casino hiding a heap of addicts.
What else? You were right about the setting here: the way you used it was breathtaking. Yes, I think breathtaking is the right word. It's not just that I could see things, but I could feel them - feel the mood projected by them, almost. The description in this story was thorough and really vivid; I saw the silver cuff links and felt that warm wind. The characters, too, were realistic and well-depicted - and never overdone or oversimplified either, which was good. You wrote a good amount of detail, but you also left enough to the imagination of the reader, which is something I've yet to master.
Oh - and the symbolism of the coffees was really cool, too. "Back then, although sweat would glisten on their limbs after work, without fail they would make the steep ascent to Smit’s village and laugh at each other’s jokes over a cup of watery coffee. By now, Kenji’s palate had experience creamy cappuccinos, aromatic espressos and luxurious lattes, but the smile was gone." I loved the comment that part of the story made: about the simple purity of the working class, and about the effect glitter has on one's perceptions of that. (On a slightly related note, I kind of screamed "No!" in my head when Smit got the five coins. I thought for a second that he was going to become an addict, and this gambling cycle would continue, from Kenji to him. Maybe that's actually what did happen, because you left the ending slightly open, I suppose. But I hoped he would take the money for the food and then never go into a casino again.)
Apart from general laziness and procrastination, I'm not sure why I didn't read this sooner. I admit that the opening paragraph didn't really grab me, so I didn't get immediately suckered in. If you do a further revision, that could be a possible thing to look at, as well as the slight ambiguity of the ending. But to be frank, I don't know if this needs any further revision. It was slick and well constructed - and even though there wasn't outright "action", the tension was well-maintained, and there was suspense - I didn't know whether Kenji was going to lose control and backslide or not. The fact that the conflict was within himself kind of means (though not necessarily) that the tension will be internal rather than manifested in an action scene - but there was tension nonetheless.
All in all, seriously good job; this is a brilliant piece of writing, Ada.