Kosaka kiosuka, the usual seventeen-year-old high school student, did not get along with his younger sister Kirino for many years. Longer than he could remember, Kirino ignored his arrival and care and looked at him with contemptuous eyes. It seemed that the relationship between the kiosuka and his sister, which is now fourteen years old, will continue so forever. Once, however, Kyosuke finds a DVD Case Magic Anime Girl called Hoshikuzu Witch Meruru (Stardust Witch Meruru), which fell in the entrance of his house. To the surprise Kyosuke, inside the housing, video game for adults called Imoto to Koishi Yo! (Love with a little sister!) He is hidden.