, short for and also known as , is a Japanese
light novel series written by
Tsukasa Fushimi, with illustrations provided by Hiro Kanzaki. The series includes 12 novels released between August 2008 and June 2013. A
manga adaptation drawn by Sakura Ikeda was serialized in
ASCII Media Works'
Dengeki G's Magazine. A 12-episode
anime adaptation produced by
AIC aired in Japan between October and December 2010. Four additional episodes, which offer a different ending to the broadcast series, were streamed monthly via the official website and other video streaming sites between February and May 2011, before being released on Blu-ray Disc and DVD in June and July 2011. A 13-episode second anime season produced by
A-1 Pictures, titled
Ore no Imoto ga Konna ni Kawaii Wake ga Nai. (with a period at the end), aired between April and June 2013. An additional three episodes were streamed online on August 18, 2013.