Fudanshism
Alternative title: Fudanshi, Fudan Shizumu, Fudanshizumu, Fudanshism - Fudanshi Shugi
Story Overview
The brother is asked to substitute for his sister as an attendant at a doujinshi convention, disguised as a loligothic girl. There he meets a girl from his class and they become friends, but he must crossdress in order to be with the girl. (taken from Baka-Updates)