Nogizaka Haruka no Himitsu : Cosplay Hajimemashita [JP]

Nogizaka Haruka no Himitsu is a Japanese light novel series by Yusaku Igarashi, with illustrations by Shaa. The series originally started serialization in MediaWorks' now-defunct light novel magazine Dengeki hp on June 18, 2004. The first novel was released in October 2004, and as of January 2012, 15 volumes have been published by ASCII Media Works under their Dengeki Bunko imprint.

A manga adaptation by Yasuhiro Miyama was serialized in ASCII Media Works' Dengeki Moeoh between the October 2006 and August 2010 issues. An anime adaptation produced by Studio Barcelona aired between July and September 2008; a second anime season aired between October and December 2009. A visual novel for the PlayStation 2 was released in Japan in September 2008 and a second game for the PlayStation Portable was released for digital download in February 2010.