So I really like this, but I've found a couple of breaking points:
1.) Like other people have said, if Chara/Frisk gets too low on health, he eats a legendary hero, and then the game freezes and I can't act except to reload. I had to nudge him down a bit, and then spam the enter key to take him out. And then, of course, he reloads, but that's a given.
2.) I made the game pretty much lock up by accidentally fat-fingering the 1 and 2 buttons while trying to reload when I got hit. It locked into a pattern of click...click...click...and now it's just a black screen when I hit 1 in the middle of that.
There are a couple of bugs, in other words, but it's a really solid concept and I enjoyed this.