is a japanese light novel series. it was written by nagomu torii with illustrations by tomoyo kamoi. the work won an honorable mention in the kyoto animation award competition in 2011. kyoto animation has published three volumes since june 2012. there is an anime television series based on this light novel series. it was produced by kyoto animation. it aired in japan between october and december 2013. an original video animation episode was released in july 2014. a two-part anime movie was released in march and april 2015.