Wow. Oh my god, wow. I am speechless. That was amazing, wonderful, FANTASTIC! This is perhaps some of the best fan made Deltarune content I've ever seen, and I've seen A LOT. I'm particularly impressed by your skill with game mechanics. The Panic Meter, whipping out the battle HUD outside of battle, and holy crap FRIEND's attacks were sublime. Really frenetic, signposted well, and creative as hell.
Also wanna spotlight that tree's text after the fight. At first I thought it was a bug the way it went off screen, but DAMN did it feel clever realizing that was intentional. Seriously added to the creepy factor.
Loved it, loved literally everything except I think FRIEND had too much HP but that's literally it. You've got an honest to god career ahead of you in game development, this would be one hell of a portfolio piece.