Because I Dont Like My Big Brother at All!! (2011) Anime Watch

Second-year middle schooler Nao Takanashi loves her older brother Shuusuke to the point where she has developed a brother complex. Wanting her brother to see her as a woman, Nao makes advances toward him on a daily basis, which often results in Shuusuke succumbing to and encouraging more of her teasing.

One day, while throwing away porn magazines from her brother's room, Nao finds an album containing his childhood photos—none of which include her. Having discovered the truth behind her family relationships, Nao becomes ever more affectionate toward Shuusuke. However, it does not take long for her dreams of monopolizing her brother to be put in jeopardy.