Don't feel bad for publishing this! For a first game, this is pretty amazing. You should see some other games that get posted here in all seriousness. Short doesn't mean bad and you really put some good work into this.
Although the story itself is quite simple (it's A Simple Quest after all), you do show a storytelling talent – in the dialogue, distinctive characters etc. That's probably what I enjoyed the most.
The graphics and music are also quite neat.
My major complaint would be probably about lags. I am not sure what you can do about it, but sometimes the game plays without any problems, and then, after visiting a village or a castle, moving on the world map becomes terribly slow and laggy. When that happened (about 50/50 chance), I wasn't really in mood for exploration and just took the shortest path to the next objective. That hinders the gameplay quite a lot.
Then, just some suggestions:
– A "shortest path" could be another thing to improve. When moving with mouse, you walk in L shapes, so if you need to go diagonally somewhere, it is quite noticeable and you follow much longer path than you would with arrow keys. It might be better to do something like "imagine a line between you and your destination and walk through all squares it crosses". Perhaps. I don't know how it would work out in RPG Maker.
– Balanced combat. I know this is because the game is short, but just in case – throughout the game, I never felt like using my special abilities or choosing anything else than "Attack", because all the enemies both on the mainland and in the cave fell with one hit.
The only exception was the Demon King who had his difficulty set just right (he's the final boss, after all), but he was the first enemy who required the use of anything besides the basic attack. So after loads of "super easy enemies" you meet a "hard boss".
– During combat, you should probably see your action right after you select it, or it gets confusing. You should attack when your turn comes and you click attack, not later with all the others. The prime example here is the Demon King – I see I am running out of HP, so I select Heal, but before my character has even a chance to cast the spell, the Demon King cast a Fire Pillar and kills her.
It should probably go like this: Demon King casts Fire Pillar, then I get to choose Heal spell when I see the actual number of HP I have – and it gets cast immediately, so I am ready for another attack from the King.
– Since the enemy sprites flash, you probably don't have to append "A" and "B" (Slime A, Slime B) to them. It might slightly break the immersion. And it could be handy to be able to attack an enemy by clicking on its big flashing sprite, not just on its name (I caught myself trying to do this a couple of times)
– And lastly, if your characters are both fine at the end of a combat, you shouldn't probably mark them "Dead" when they run out of HP. "Defeated" might be more appropriate.
I am not really a fan of this style of turn based combat and enemies popping out of nowhere (but many people are!), it was your story that made me wonder how the game ends and finish it despite of the lags. And if this is just a practice you feel "a little bad about", then I know when you make a game you'll be proud of, it'll be awesome. So good luck with that. ;)