That Time I Got Reincarnated as a Slime Novel Volume 12 is written by Fuse with illustrations by Mitz Vah.

Threatened by Tempest’s rapid expansion, the Eastern Empire finally begins to strike back. According to Chloe, the time-traveling Hero, there exists a timeline in which the Empire defeats Rimuru and Tempest subsequently collapses. While Rimuru’s doom isn’t set in stone, his victory isn’t a foregone conclusion either. And to make matters worse, an Empire spy seems to have infiltrated Tempest...