Moteuchi Kei is a shut-in who spends his life playing "Isekai Harem Paradise", an online fantasy game full of cute girls of various races, from succubi to elves and others. Alas, the game is set to shut down in a week, to Kei's dismay. What he didn't expect was to be summoned into the game's world by its characters, along (accidentally) with three of his classmates. He's now the only one who can save that fantasy world he knows so well… but the succubus Désir, who summoned him, seems to have other plans.