Finished the game in just over a week of regular gameplay! I got what I suppose is a pretty good ending, though I don't know if it's the best one, since I don't actually know if other endings are possible.
Some final thoughts:
I felt a little frustration in the necessity of backtracking and revisiting areas, particularly in late game when save points become very rare. There are also a few late-game quests that are difficult to achieve compared to the reward they provide.
But, these are very minor detriments to the game. Graphics are stellar, with a lot of lively detail, especially given the Game Boy limitations. The characters are engaging, and some of them quite fun, so that befriending them feels natural and rewarding, with a tone similar to Undertale. Music is pretty good, a touch repetitive but I never felt bored by it. Sound effects are basic, but serviceable enough. The storyline had enough mystery and plot development to feel good enough to draw the player in to continue to learn more. Dialogue is quite natural and sometimes pretty funny. The puzzles aren't too complex, but do force you to think through some actions and keep some notes. While I only played through once, there seems to be enough flexibility in the custom character design to fit a few different styles of play.
Overall, this was incredibly entertaining-- if a game like this had been released during the actual Game Boy era, it would have been a smash hit. Nothing in the game was jarring, or out of place, or felt forced, and I never felt like I was wasting my time aside from the (occasional) late game backtracking. You've really got something special here! I saw your retrospective post on feeling a little deflated, but given what work you must have put in, that's only to be expected. But believe me, this really is one of the best homebrew games I've ever seen for Game Boy. Thanks again for making this!