That... was... AWESOME. I need to complete the Asriel romance, but I just had to follow my heart and romance my vertabaes first. From what I remember of the original Underfell AU, before I drowned it in reader-insert fanfic, everyone feels so faithfully rendered. Your writing was charming and captures the essence of Undertale and this AU as magnificently as a fan-author possibly could.
I'm very excited to try out the other ones. You are a delightful writer. May you remain filled with DETERMINATION!
[P.S. I think there was an error. It looked like there was meant to be an input during the Post-Judgement scene in the Judgement Hall with Sans. I don't know if I have a save before it, but if I do and can recreate it, I'd happily supply a copy of the save to see what went wrong.]