How Not to Summon a Demon Lord: Volume 2, Paperback

The second volume of an adventure with an earth-shakingly powerful Demon Lord (or at least someone who acts like one) taking on another world
After being summoned to another world that resembled the video game Cross Reverie, Takuma Sakamoto accidentally ended up with two girls as his slaves: the Pantherian, Rem, and the Elf, Shera. Takuma, under the guise of his screenname Diablo, came to this world a powerful Sorcerer, just like his avatar in the game. Along with the two girls and Emile, a devilishly handsome Warrior, they managed to protect the town of Faltra from the looming threat of invasion by the malevolent Fallen. But that peace they brought upon the town did not last long. The Kingdom of Greenwood, a country of Elves, makes a troubling demand: if their princess isn't returned to her rightful home within the time allotted, then the Kingdom will declare war on Faltra-- And it's up to Diablo and the others to prevent a war with the Elves