京都アニメーション
The series began as a light novel series written by Torako, with illustrations by Nozomi Ōsaka. Torako entered the first novel in the series into the first Kyoto Animation Award contest in 2010, and it won an honorable mention in the novel category. Kyoto Animation published four volumes under their KA Esuma Bunko imprint from June 2011 to December 2017.