[gonna try to do a pretty simple one to get back into it since its been a month and a half and stuff.. so it probably wont be that good]
If your idea behind it is good, everything else can be worked around.
If your idea is
not good, it's a one-shot anyway and can be used to learn with. Either way, you get something out of it. I don't think anything you have written so far has not been good though, so don't worry about it!
"I was supposed to be off fighting the gym by now...", I grumbled to myself, stumbling through the forests outside Violet City.
This section here should be its own paragraph spaced apart from the next section below.
Hmm! So our protag here is having difficulty with something.
I had made the mistake of trading one of my two mons for a overleveled Eevee, forgetting the badge requirement, and it bolted the second I let it out of its ball.
"over-leveled" i think might look better here.
Oh! Clever that you are exploring the concept of badge requirement here! I always enjoy how you take different concepts from the game and flesh them out for how they would actually work.
That was 3 hours ago. At the very least, I had my Pokegear on to some music, to pass the time.
That Eevee is GONE!
Just when I was starting to wonder if I was lost, the grass had given way to stone. I had heard of some research expidition nearby, but I had no idea it was so close. But, if there were people there, maybe they would've seen where my traded Eevee went!
"expedition"
Yeah, at this rate, anything is worth a shot to find that Eevee!
Ignoring how out of place I appeared around these researchers, I went up to one and confidently inquired whether they had seen my mon nearby.
So, I have an idea here. It's a bit of an advanced writing technique. (Or at least advanced for me.) When you said "confidently" instead of saying that, show us what confidence looks and/or sounds like. Maybe give us dialogue to display it. It's a way to add more depth.
How you have it written isn't bad though. I don't want you to get that idea.
In the past I haven't suggested these types of things to you because I was focusing on the things that needed the most attention. Your writing has been improving, so I find it easier to pick at less pickable things if that makes sense. I also don't feel like providing too much concrit at once is good for a developing author. It can be discouraging. Feels much better to develop in steps along the way, I think.
"Well, there was a Eevee nearby with a blue ribbon, but we didn't pay it any mind. I believe it wandered into one of those ruins, but you would legally need a scientist to accompany you if you wanted to go rescue it."
On the topic of depth, you can enhance this further if you give the scientist a description or provide an action to accompany the dialogue. As it stands, we don't even know their gender.
Again, this is not a huge problem or anything. As it stands, I imagine a male scientist with a lab coat, balding, skinny, and with glasses. I'm just having to stretch a little more to try to find useful things for you.
Regarding the content of the bit above, I wonder why they would have such a requirement...
Shoot! I didn't know a lot about ruins, but I had seen enough movies to know they could be pretty lethal.
This line should be separate from the bit below.
Swallowing my fear, I asked, "C- could you accompany me then? Having the extra firepower would be nice, even if I COULD handle myself in there."
Great job on this line. I think you could add to the effect by adding two more dots at the end if you like.
"Arright, I was scheduled to research that section anyways, so I could help you look for your little guy, kid." Phew...
Did you mean to spell it as "Arright"? Seems like it might should be "Alright"
"Phew..." should be it's own separate line.
Ok, so the protagonist gets a sidekick. Suddenly I am reminded of Rick from my fic lol...
The inside of the ruins was as claustrophobic as I imagined, though quite a bit smaller.
Just how small IS this? Are they having to crawl on the ground to move around? Are the passage ways very narrow? These questions can be a good signal to expand upon the detail here.
Despite it being a singular room, the light hardly made it past the entrance, and the flickering of torch light was the only thing shining in that room. Despite the warmth, a chill ran through my spine.
Here is another writing trick I can help with. Try to avoid using the same word too often in a short span of words. You have "Despite" used twice here. Example, you could switch out the second and reword like this "The torch radiated warmth, but a chill ran down my spine anyway." (I thought it sounded slightly better. Up to you though.)
Avoiding noticeable repeats can add subtle quality.
"Are you sure they went in here? I don't think there's anywhere they could've hidden...".
"I'm sure of it... maybe they... aha!"
This section was a little vague who was saying what. I was not used to either character enough to be confident which dialogue belonged to whom. I correctly guessed the bottom was for the scientist, but it was a little distracting. A dialogue tag added to either line would probably solve it.
You can take out the period at the end of the first line.
Also, each line of dialogue should be in it's own paragraph with spacing above and below it.
The dialogue itself looks good though!
The researcher dramatically pointed to a panel in the middle of the room. "You can see some paw prints in the dust there... d- did they solve the puzzle here already?"
This section here should have spacing both above (if it didn't already) and below.
The dialogue itself seems a bit odd. Maybe try something like this? "There! I see paw prints in the dust on the panel... d- did they solve the puzzle here
already?"
"What, you were outsmarted by a POKEMON?!"
This line also needs spacing both above and below.
Also, I would recommend switching the comma to a "?"
"No... w- we just hadn't gotten to properly researching yet... it takes a lot to set up a research base, you know!!"
Sure Mr. researcher (who isn't confirmed to be male). I
totally believe you...
They pushed around the stone on the tablet, mumbling to themself, while I watched over their shoulder. All of it went over my head, but I was curious. Unfortunately, that turned out to be the wrong move, as the floor literally fell out below us.
Oopsies! 😅
Thankfully, it wasn't a long drop, so we were just bruised up slightly.
This line should probably be its own line.
The researcher, however, was elated, and hopped up. "I KNEW there had to be more to these ruins! Let's look around for your Eevee, then!"
This should all be it's own line.
I wonder how the Eevee found it's way down here? So spooky!
Looking down, I had noticed my Pokegear fell out of my pocket, and was eminating some horrible staticy noise.
"emanating"
Instead of "staticy noise" you could cut a word out and make it "static"
I went to turn it off, but he grabbed my hand. "Wait- this could be attracting some mystical Pokemon!"
Should be a separate line here. Any time there is dialogue, both the dialogue and dialogue tag should take up it's own paragraph even if that paragraph is only one line.
Why would the scientist think the static would attract a mystical Pokemon??
I didn't really think any would appear, but their face was stone cold, so I left it on.
Stone cold seems an odd word choice here. Makes me think they are no longer living.
I can't think of something to change it to though. Maybe I'm just sleepy right now.
Thankfully, the little Eevee was close by, and cowering in a corner. They seemed to recognize me, but seemed too scared to run away and disobey again. "Great, we found em! Now, I always keep an Escape Rope on hand, so we can just-"
Wait, so Eevee got down there NOT intentionally even though it took some intelligence to pass the puzzle? Hmm...
Also, you used seemed twice in close proximity. You can cut out the 2nd "seemed" entirely and it looks like it doesn't lose any meaning.
An inhuman screech eminated from behind us.
"emanated"
Also, this should be spaced apart from the other things as it's own line.
Well! If Eevee wasn't scared before, I bet they sure are
now!
I guess they weren't too far off, we really were about to run into some new pokemon.
I really hoped the researcher could fight, because my only mon was the misbehaving Eevee.
These two sentences can be part of the same paragraph. If they are on different paragraphs with no spacing between them, it would be better to add spacing between them. Probably better to have them share a paragraph though.
Let's go reasearcher you can do it!
Strangely, the mon before us seemed to resemble a.... A.
Should be "an" not "a"
The letter. I was still terrified, but the researcher excitedly threw out their mon and began fighting. I slowly backed up and tried to comfort the mon, and plan our escape.
Probably would work better if you called the 2nd "mon" Eevee instead. I assume they are not trying to comfort the mon of the researcher.
Also, I wonder what mon the researcher is using? I'm imagining a Magnemite.
"Help!!!" Whipping back, I saw a horrific scene- the researchers mon passed out on the floor, and the man himself pinned down.
This part should be it's own paragraph with spacing above and below.
Ah ha! "Their" gender is now revealed to be a man! Because apparently one just
isn't a man until they yell "Help!!!"
But what was the researcher pinned down by? Did his mon fall on him or is the opponent pinning him down?
Without thinking, I yelled out, "Eevee, use Headbutt!".
This can be its own paragraph with spacing both above and below.
And you know what? They actually listened. The Eevee cleanly knocked the mystery mon off them, and I followed up by chucking a empty PokeBall at them.
"chucking
an empty"
No need to use "them" to describe the man at this point if you don't want to. You could use "him" now instead. Also, the way it's written could be interpreted as throwing the Pokeball at the man instead of the Pokemon...
Glad Eevee listened for that! Without it they would have become Unown food!
"Phew, I was worried I was going to be killed. If you need a favor, I can try to help."
Wait, so the Pokeball was chucked, but did it hit it's target? Even if it DID hit, was the Unown successfully captured?
This also should be it's own paragraph.
Wow, this scientist is
so grateful that when you save his
life and he will
try to provide a favor!

Maybe "If there is any favor I can do to repay you, just let me know!"
"Well, there is one thing... can you trade the weird letter mon for a lower levelled mon?"
Wait, so the issue is with having a mon too high of a level, and the protagonist wants an even higher level mon to replace Eevee?
Also, spacing/paragraph here too.
"Sure, but it seems like yours is starting to trust you more!"
Spacing here too.
Sure enough, looking down, I saw the Eevee rubbing their fur on my leg. Maybe we could take on the next gym.
Aww it's grateful to their savior! Great way to end it!