Ore no Imouto ga Konna ni Kawaii Wake ga Nai

Story

Kyousuke Kousaka, a normal seventeen-year-old high school student, hasn't gotten along with his younger sister, Kirino, in years. For longer than he can remember, Kirino has ignored his comings and goings and looked at him with spurning eyes. It seemed as if the relationship between Kyousuke and his sister, now fourteen, would continue this way forever. One day, however, Kyousuke finds a DVD case of a magical girl anime entitled Hoshikuzu Witch Merle (Stardust Witch Merle), which had fallen into the entrance way of his house.

Synopsis via AniList (English).