Masamune Izumi is a high school student who writes light novels.

Sagiri Izumi is a shut-in who never leaves her room.
A year ago, she became Masamune’s little sister.

But one day, Masamune discovers a shocking twist—
The artist "Eromanga Sensei," who has been drawing illustrations for his novels, is none other than his little sister Sagiri!

His cute little shut-in of a sister, who has been living under his roof, is using an obscene pen name and draws lewd illustrations?!

This slapstick comedy about a light-novel author big brother and his little sister the illustrator brings a cast of charming characters surpassing even that of “Oreimo!”