Menu
Not my favorite design, but my biggest issue is the Location section where the words are so small reading the name can be a pain.
Intro
Not too bad, but there were things you could fix. During the introduction, you have characters moving randomly which makes it look a little amateurish. If they're really needed then try to give them a definite path; they're not there for long so it shouldn't take any time to program.
Right off the bat with the confrontation between Minerva and Aastra I got the feeling of exposition; I felt the conversation was there simply to explain things to me, not to sound like a natural exchange, something that continues for the rest of the introduction. I get the feeling Aastra's supposed to come off as crazy but you're forcing it. Giving a glimpse of his personality and revealing the rest through the story might work better. You have some grammar problems and the text box shaking I could have done without. There was too much of it and I don't feel that it really added anything of value.
The transition from 500 Years Ago to Present Day was too abrupt and could have been smoother by stretching out the fading of music/screen color for a few seconds. Spelling error with the king ("You were sleeping again?" and numbers should generally be spelled out), and using the slider to change the colors of the soldiers doesn't work very well - they come out looking maroon in the face. The throne room doesn't strike me as a throne room; the water feature is odd and there are two many statues, too close together. The king and player are clearly having an argument but I'm not feeling it. Maybe if the music changed (it's too happy) or you somehow showed the sprites getting frustrated - altering the main characters features to look angry isn't too hard, if I remember correctly. Surge's picture also isn't as high quality as the others but I don't know if that's because the site you got it of or something else.
Eternity Castle
From a purely financial standpoint, letting the prince into the treasury probably isn't the best idea. Giving him a set amount of money and supplies would probably be more realistic.
In the prison, carry the wall tiles over the doors. There's also too much decoration; it's a prison and while you're trying to give that feeling with the mice and whatnot, you're also taking away from it by adding suits of armor, random pillars, pictures, and weapons - my sister thinks it's perfectly okay to have them but I question of the wisdom of having them so easily accessible. What if there's riot?
The game crashes when you try to go to the rightmost room; there?s a graphic missing for one of the people on the beds.
First Impression of Battles
For game difficulty, I'm on normal and convinced that you've made your enemies much too strong. It wasn't a matter how me taking to long to plan my moves, it was a matter of each hit from a bee taking one fourth of my health. Everything acted faster than me so by the time I got in one hit every other enemy had already given me two. Giving their skills such a high cost rate wasn't smart either; starting skills are tricky, but generally you give them enough power to be useful and low enough cost that they can be used effectively - not spammed but also not worrying about having to save it because you can only use it once. For the sake of making it through the rest of the demo without having to restart on a lower difficulty level I went into the editor and raised my stats.
Your end of battle screen is also a bit cluttered with the item and experience boxes overlapping.
Earth Shrine
A few gripes about this: I have no idea how long it would take to defeat the Elemental normally because, as I said before, I edited my weapon/armor stats to make the battles more bearable. Having her heal for five hundred, however, while I was normally taking off a very small portion of her health is very annoying. Her dialogue does not strike me as being a powerful being and the reactions of Surge and Player left me lacking. This is obviously a strange, shocking event, shouldn't their conversation reflect this.
After beating her, the following scene went awry - during the flashback with the angels I suggest either changing to the music or shutting it off completely, though temporarily, for impact. Happy, bouncy field music doesn't cut it for that scene or the Shrine itself, which I thought might be more somber and mystical. There are plenty of sources to get more fitting music.
The Player's graphic was wrong when he was getting back up; for a while he was the green-haired thief, but setting 'fixed direction' will take care of that.
Because I can walk through the mushrooms on a log, I am then able to wander around the map at will. This is a mapping error that should be fixed.
Mountain Path
The shadow script really stood out. I considering this a risky thing to use considering all the problems that can come up with it normally, but in this location I noticed them on nearly every map because of how they interfered with passibility.
These take away the illusion of height difference, interfere with normal mapping, and there are errors where I can travel to areas I'm not supposed to.
Harpy Queen
When the Player and Surge are looking around for the Harpy Queen, I suggest actually having them spin around so their actions match their words. There's also a gigantic amount of blood and a severed head, yet the two don't comment or give it a second look. Even a quick mention before entering battle would be better than this.
Ruins
Immediate mapping errors: don't just copy and paste the grass tiles. Square grass doesn't cut it and the tiles you're using are actually made to connect corners.
I'm a little confused as to how Surge knew who was talking, considering the fact that they never saw who was behind the wall. Despite the fact the people they're talking about haven't left the mainland in nearly five hundred years, the king accepts his thoughts without asking any evidence. While I'm sure he trusts Surge, something like that might require more than just "I'm sure"?
Castle Right After Ruins
Remember to use actions to support your words - when Derrick is yelling at the king to rethink his decision, he's still facing the player. Making him turn to the king would add to the scene.
The king could have at least come with an excuse to why his son couldn't go. There are, after all, plenty of good reasons: he's the only heir, he's inexperienced, he needs to be there to support his mother, etc?
Now that I'm able to explore the castle at my leisure, I'm finding some more odd mapping. I assume you're trying use the water autotile as an accent in the rooms, but it just comes off as misplaced. Don't use the thrones too casually since it takes away from their importance. Having them in the dining room is okay since those are their designated spots, but having them in the guest room is odd.
The mess hall kitchen needs some serious work; expanding the middle of the counter doesn't work. Rooms don't have to be perfect squares/rectangles, so maybe change up the design a bit and add some counters.
The princess's dialogue is screwed up - there are marks in the conversation that shouldn't be there. Also, is she a visiting princess or the player's sister? The guests, who are obviously important enough to have rooms in the castle, are never explained.
Watch how you use your text headers; I spoke to the queen before talking to the soldiers at the front entrance and now each other them has her face and name. The same thing happened with the prisoner.
The fact that there's no choice but to let the prisoner out bothers me. If it's really so important that he be released, maybe you could at least give the player two choices (immediately free him or try to pick the lock/something) and have the other lead nowhere. Right now I can't help but think what an irresponsible prince this kid is.
Opening the chest in the ruins, after going through the big room and climbing the stairs, froze my character. The graphics were still working but I couldn't move and had to shut the game down.
There's also a graphic missing when you try to enter the sealed cave. This was doubly annoying because I had transferred all the files onto another computer that didn't have RPG Maker installed and had to go back, fix it on the first computer, and transfer it again to continue working comfortably.
Something really strange happened when I went into the cave - there were two of me. I'm pretty sure you made an event of the player and didn't move the player himself.
That's one unconcerned trader.
When I was trying to enter the second cave room, I once again found a missing file, this time a waterfall sound. Might be my fault - maybe when I transferred everything, I somehow missed it. Either way, I skipped that part and set myself right into the ceremony room so I could finish the demo.
Couldn't find the 'laughing_man' sound either, edited it out to complete the fight. After he killed me, the graphic for both the player and Surge's down positions were wrong.
After that scene the screen went black for so long, I went back into the editor to see what happened next. After not being able to trigger the next scene I finally stopped. I figured you'd be happier getting a partial review than waiting for me to figure my problems out. Personally, I think Surge's and the King's deaths would have been a nice place to stop for the demo.
Overview
The text speed is a little slow, especially in scenes that are supposed to be frantic or urgent.
Personality wise, I find both the Player and Surge to be a little bland, the latter more so. While the Player obviously resents having to carry some much responsibility, Surge is...boring. I'm not sure if that was intentional or if it just came across that way but you might want to try and work on that. Since you're killing him off you want the player to grow fond of him and really show the friendship between the two in order make that scene have more impact.
The story's not bad - sure it looks a cliche at first, but you've said you're trying to take it in a different direction and there's still time for that. Still, most players judge a game by the beginning and might be turned off by the plot they're seen so far.