That Time I Got Reincarnated as a Slime Novel Volume 8 is written by Fuse with illustrations by Mitz Vah.

It's festival time in Tempest, and this exuberant ectoplasm knows how to throw a party! After reconciling with Hinata and securing his title as demon lord, Rimuru's pulling out all the stops to hold a massive bash in his nation of monsters, along with a little help from his many friends and allies!