Time Stop Hero Vol. 13 by Yasunori Mitsunaga

The chief of the elves has been murdered while alone in a locked room?! Sekai is on the case, and thanks to his knowledge of Earth's mystery fiction and his incredible power to press pause on the world in which he's trapped, he solves the crime! But it's much harder to find a solution for a threat that may lead to the annihilation of all the elves. Can Sekai save the day and clear this deadly level?!
Binding: Paperback / softback