is a japanese light novel series. it was written by kana akatsuki. the drawings in the book were drawn by akiko takase. it won the grand prize in the kyoto animation award in 2014. this was for novels. this was the first time something had won a grand prize in the kyoto animation award. kyoto animation released the first book on 25 december 2015. they released it under their ka esuma bunko company. an anime television series came out between january and april 2018. an original video animation episode came out in july 2018 and a movie will come out in january 2020.