Bored with life and considering the real world to be just a “crappy game,” savvy sibling shut-ins Sora and Shiro have withdrawn into their own fantasy world filled with video games. However, one day they find themselves summoned to another world by a boy who calls himself “God,” their abilities are about to be put to the ultimate test! Now not only their fates — but the fate of all of humanity — will be decided by a series of games that may just be the hardest these super-geniuses have ever faced!

Masamune Izumi is a high school student who writes light novels. Sagiri Izumi is an antisocial girl who never leaves her room. A year ago, she became Masamune's stepsister. But one day, Masamune discovers a terrifying revelation: the artist “Eromanga-sensei,” who illustrates his novels, is none other than his sister Sagiri! His antisocial little sister, who lives under the same roof as him, uses a spicy pseudonym and draws obscenities?!