How Not to Summon a Demon Lord

After being summoned to another world that looks almost exactly like the MMORPG he once played, Takuma Sakamoto now spends his days going on adventures with Rem Galleau, the black-furred Pantherian, and Shera L. Greenwood, the Elf princess, both of whom accidentally became enslaved... to him!?One day, he is suddenly approached by the Fallen, Edelgard, with a request: Would he help her to undo the seal that keeps the Demon Lord Krebskulm inside Rem?Takuma, under the guise of his in-game character Diablo, hesitates, as he had previously made a promise to Rem to help her defeat Krebskulm— But he pushes through with his Demon Lord role-play and actually agrees!＂I will revive the Demon Lord Krebskulm—and defeat them!＂Now it’s his Demon Lord role-play vs. an actual Demon Lord!