 The cell phone novel "Tenshi no Koi", which revolves around the topic of female high school students, had 13 million readers in Japan as of July 2009.On 19 July 2009 it was announced to the media that the novel would have a film adaptation and that the main cast members would be popular model Nozomi Sasaki and professional actor Shosuke Tanihara.In her first lead role in a film, Sasaki was cast in the role of Rio, a seventeen-year-old high school student, while Tanihara would be her co-star, playing Rio's 35 year-old professor Kouki.