Oreimo(2010)

俺の妹がこんなに可愛いわけがない

Oreimo follows the daily life of an ordinary high school boy named Kyousuke Kousaka. Kyousuke’s younger sister Kirino is a pretty fashion model, but also hides a dark secret of being an otaku of adult games. Kyousuke is the only person to whom Kirino reveals her hidden obsession and other issues.