Eromanga-sensei centers on light novel writer Masamune Izumi and his shut-in stepsister Sagiri, who are still trying to rebuild a normal family life after losing their parents. Masamune depends on a mysterious illustrator called Eromanga-sensei, whose provocative artwork helps his books stand out, but the partnership turns awkward when the artist's identity comes to light and the two siblings are forced to face each other not just as family, but as collaborators.
From there, Eromanga-sensei mixes domestic comedy with the pressures of the light novel industry, following Masamune as he races deadlines and Sagiri as she slowly begins to step back into the world outside her room. The series keeps their home and creative work tightly linked, so every new project, misunderstanding, and public success tests their pride and dependence in equal measure. Around them, rival author Elf Yamada and the rest of the creative circle add friction, competition, and support, giving the story a broader look at how young writers and artists chase recognition while learning how to trust the people closest to them.