That Time I Got Reincarnated as a Slime Vol. 11 (Kodansha, 2019)

Rimuru's taking a break from managing his kingdom of monsters by honoring the memory of his friend Shizu. Her former pupils will perish if he can't find a way to rein in their unstable magical energy, and he might just have the answer. It will involve enlisting the help of powerful elemental spirits-but he's about to find out that their fairy queen is a bit of a loose cannon...