That Time I Got Reincarnated as a Slime, Vol. 11 (light novel)

Rimuru and his team are headed for the Holy Empire of Lubelius to organize the concert he promised Luminus, its leader. But as preparations continue, a fiendish conspiracy involving both demon lords is being laid out behind the scenes. There may not be much time for music after all…especially with a third demon lord on the hunt for a certain otherworlder in Rimuru’s care!