Ore no Imouto ga Konnani Kawaii Wake ga Nai.

Synopsis

As Kyosuke, Kirino and Ruri decide to visit Saori's apartment as a surprise for her birthday, they finally see what she looks like without glasses. Four years ago, Saori was a weak bodied girl who was shy about showing her face to others. One evening, she was brought by her older sister, Kaori, to a special apartment where she indulges in otaku activities alongside her flatmates, Shinya Sanada and a budding manga artist named Kanata Yamanashi. Kanata took an instant liking towards Saori and soon taught her about the otaku lifestyle. However, the circle soon starts to dwindle after Kaori left to get married, leaving Saori alone once more. Feeling betrayed by Kaori, Saori became determined to start her own circle and help others like she helped her, receiving her trademark swirly glasses from Kanata to help her on her way. This would eventually lead to the start of her otaku life and her meeting with Kirino and Ruri. Back in the present, Kaori, Kanata and the rest of the old gang also show up to check up on Saori's new friends. After Kanata reminds Saori to pass down her glasses once she doesn't need them anymore, Saori begins her birthday party.

(Source: Wikipedia)