"The MMORPG Cross Reverie's top player, Takuma Sakamoto, is summoned to another world and forced to play the role of the Demon Lord Diablo! After purchasing a new set of rings with Sylvie's help (and completely unrelated to a certain coupon he got), Diablo visits the capital. But he becomes involved in a certain incident at the sorcerer's academy and ends up attracting the attention of the Order of Palace Knights. Taken to meet the king, Diablo grandly declares:
"I am Diablo! A Demon Lord from another world!"
Accepting a quest from the king, Diablo makes his way to the south, where Rem's hometown is. But when they see her family's home and business, Rem declares flatly -
"They're basically like the yakuza."
This is the eleventh volume of the adventures of an earth-shakingly powerful Demon Lord (or at least someone who acts like one) taking on another world!"