In Another World With My Smartphone: Volume 16 by Patora Fuyuhara

Still struggling to unite two worlds, fledgling god Mochizuki Touya carries on with his work. The mutants continue to attack the Reverse World, hungrily devouring the souls of the fallen in service of Yula and the wicked god. And so, it's up to Touya to teach another set of off-worlders how to pilot the Frame Gears! Hopefully he's not too late... Elsewhere, a mystery unfurls regarding a long-lost prince of a devastated kingdom... Perhaps the Mage-King of Isengard has the answers Touya seeks? Chaos runs rampant, tearing open the veil upon a story of swords, sorcery, and heterochromia!