What is "koizora"

, or for short, is a 2005 best-selling Japanese coming of age and romance novel written by Mika. Originally posted on the cell phone website "Mahō no iLand", where chapters would be released exclusively for mobile reading, Koizora received a hard print publication from Starts Publications in October 2006, with the story being separated into two volumes.

Koizora is claimed to be a biographical account of Mika, or at least, based on first-hand accounts. It boomed in popularity and became a mass cultural phenomenon, spawning a theatrical film, a television drama adaptation, and a manga adaptation.

is a 2007 film based on a cell phone novel of the same name. The film is directed by Natsuki Imai and it stars Yui Aragaki and Haruma Miura.

Koizora debuted at the Japanese box office on 3 November 2007. It grossed a total of US$36,684,020 in both Japanese and international box offices.