Haruka Nogizaka's Secret is a Japanese light novel series by Yūsaku 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.

Monthly Comic Dengeki Daioh is a Japanese shōnen manga magazine published by ASCII Media Works under the Dengeki brand. Many manga serialized in Dengeki Daioh were later published in tankōbon volumes under ASCII Media Works' Dengeki Comics imprint. The magazine is sold every month on the 27th. A yonkoma section of Dengeki Daioh called Dengeki Yonkoma Daioh (電撃4コマ大王) features various omake strips of the manga series published in it. The format is typically a normal drawing on the right side featuring one or sometimes more characters, and a vertical four panel strip on the left featuring characters from the associated series in super deformed form. Two special editions of the magazine called Dengeki Moeoh and Dengeki Daioh Genesis are sold bimonthly and quarterly, respectively.