A 2010-current light novel series by Kamoshida Hajime, with illustrations by Mizoguchi Keiji, published by ASCII Media Works' Dengeki Bunko imprint. Also adapted into a 2011-current manga by Kusano Houki, serialized in ASCII's Dengeki G's Magazine, and a 2012-2013 anime by Genco and J.C.Staff.
Kamoshida and Mizoguchi would go on to collaborate on another light novel series, Seishun Buta Yarou.