1) Patience. People aren't going to subscribe as soon as you publish it.
2) Update frequently. If you update more, more people will see it.
3) Tag it the right tags.
4) Have a proper title.
5) You could also try advertising it, whether it be at the shops or with the advertising calendar (though that takes a lot of kp).

Also, remember what you're writing for. If you're writing for yourself because you enjoy writing, then don't mind about the subscribers. I agree somewhat with what MissMinew said — the forward/description is redundant. Just because no one else had pointed it out doesn't mean she's wrong. It's not capturing enough for most people to want to read it.

I've received great advice and constructive criticism from strawberryspoon and fangirlonsteroids. I feel more inspired and my patience has increased more than ever. I made a new account to write and that's just what I'll do. Sometimes you forget why you start something you love and end up being in the mix. Thanks, once again.

tips:
1. make the title just "Thinner" and honestly i don't find it to be an interesting title but if it's inspired by Stephen King then I kinda get it...Although it would be great if you can make it unique and original to YOU.
2. if these are idols you relate to then that's great but if it's in regards to popularity then I think more people will read it if it was Hwasa x MAMAMOO member or OC X RAPMON although he's not as popular as other BTS members in fanfiction.
3. This might just be me but I really hate story chapters that have a layout. If it's a review/graphics/roleplay thing then I get it but for a story, it turns me off.
4. Your chapters are pretty short and I think that turns off a lot of readers.I think your writing is okay though. A lot better than some that I've seen on this site and have way more subs.

Your foreword is awfully boring. You keep going in a circle, saying the same over and over and over again. 'Hwasa is struggling with her hourglass figure in a society where thin is in'. That's the point.

It's also new so like fangirlonsteriods said; don't expect too much.
And the whole bribing-thing is a turn-off for a lot of people.

I think you need patience. You just published it. Subscribers won't start coming in immediately.

Also, if you say "a new chapter every five upvotes," you'll be disappointed. Not many people normally update and five upvotes is a lot. Besides, bribing your readers like that isn't the best idea.