This song is It's Raining Somewhere Else from the Undertale AU, Underswap. It's also extended. 

song by raysonwilliams

UNDERSWAP - It's Raining Somewhere Else EXTENDED (not my song)

Hello! I'm Yuri the Rin (noteflight) and I compose my own music. I've been in concert band for about 4 years. I also have been playing jazz for a while. i have no idea why name is Reiner

Drug? Yeah, i do drugs. thatoneperson8487 (Discord)
Pfp: https://aminoapps.com/c/undertale/page/blog/sans-memes-papyrus-once-again/vedS_nuwmYXVJelNn1NQYDnKW33GQgP
Header: https://imgur.com/a/5fXPx
Edited by Me.
Favorite AU - Help_tale.