I don't care how much it hurts...

Read at own cautions: I critique very hard.

Hi!I am also a fellow Flameonna shipper, and I do like your concept and deep description. The emotions are displayed overall, pretty well done!

Now: About your art:
I am very surprised this is your first time drawing flame prince and he came out really great!! I have not much to say about the characters themselves but I would recommend you make the lines smoother. If you are using paint tool sai, you can adjust the stabilizer to 10-15 to make it smooth. You could also use the lineart tool if you'd like and make curves. If those tools aren't handy to you, a good way to make things smooth is to draw lines quickly. Do it a few times until it becomes right <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="391" title=" (Smile)"/>

The art is captivating but it can turn some people off from clicking on it by the anatomy. Search up poses or other resources first if the pose is unfamiliar to you. Fionna's waist is curving in and sticking out too much and it is an unnatural sitting position. You could also make some adjustment to her neck, which is a little wide for the Adventure time style. Basically, make some more tweaking to the anatomy and it will pop out much more <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="391" title=" (Smile)"/>
I want you to recognize fi's feet, as that is quite important. a sitting person's feet will be flat on the ground, keep this in mind <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="391" title=" (Smile)"/>

Why's and so's..
Vision: 2.5
Your likeliness of the characters are right on, to the colours and clothing, but your anatomy needs further improvement to make it come to life. Note: FP is fire, he should cast off some glow to the surroundings. A famous saying I heard was something like "it doesn't matter how good your art is, as long as the pose is correct nothing else matters". And as you know, body language reflects deeply on emotions! <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="391" title=" (Smile)"/>
Originality: 2.5
I must be frank with you, it is not totally original because the pose is popular among us fans haha. I do really like how you paid mind to the details of fionna's burnt clothes and skin! It makes a lot of sense because he is fire. Next time try adding a little bit of light grey smoke to give it a "hot" feel. Great job here!
Technique: 3
I like how you shaded fionna's hair and skin! You knew the hair casted shadows, and sometimes most people would forget, thinking it was really close to her face. The jewels on FP was well done, I could feel the hard edges by the reflections. Great work here!
Impact: Wow. Fionna's tears and smile definitely got me clicking this piece! The impact is definitely deserving of a 4 because the emotions it gives to the viewer is quite great! <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="391" title=" (Smile)"/> The text you added also helps to a degree to broadcast the emotions to be shown in the picture.
Overall: Well done!

I encourage you to keep on drawing!! You have amazing talent and I'm very sure with tons of practice, you can deliver even more feels to your viewers!
In a few years you could even do a draw this again meme! Ya never know right? <img src="e.deviantart.net/emoticons/b/b…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="366" title=" (Big Grin)"/>

Any questions, you can note me or comment on my gallery! <img src="e.deviantart.net/emoticons/l/l…" width="26" height="17" alt="" data-embed-type="emoticon" data-embed-id="276" title="Love"/>