Extremely well done. Considering that the game is almost entirely crafted from the RTP, it was a surprise to find that you almost forget about that, losing yourself to the fun of the mechanics. The battle system was extremely robust, and the clever way the boss fights were crafted really forced you to have to think outside the box and utilize every ability at your disposal in just the right way. Very well executed. The only downside I could see is perhaps the length of time it takes to get to each major milestone of the story, as there is not much to really do aside from hopping from battle to battle. Then again, that is the point of the story arc, so I suppose that is not technically a downside.
The RTP is obviously something that you could consider replacing with more aesthetically pleasing resources, but the game really doesn't need it. The only bug I could find was with the Foresight during the Volcano Lord fight. Even when I only did it once, it still seemed to occasionally hit another enemy target. Not a huge issue though. I only got about two hours in, but it was fun and engaging. All in all, a really solid entry.
Here is a completed Let's Play: