That Time I Got Reincarnated as a Slime, Vol. 15 (light novel)

After a fierce battle, Veldora has fallen into the enemy's clutches, and Rimuru is
furious. The order comes down to unleash a massacre, and Benimaru and the other
Tempest executives couldn't be more thrilled. The fuse has been lit for the final battle
between Tempest and the Eastern Empire. But if he wants to save Veldora, Rimuru will
need to evolve even further. It's time to release the power he's been holding back!