Director Tatsuki has been posting a short anime clip on his official Twitter every month since January of this year.
The TV anime is based on his independent short anime of the same name produced as the fourth title of his doujin anime circle irodori in 2010-2012, and is set to premiere on BS Fuji in January 2019 and will be streamed exclusively on Amazon Prime Video.
The voice cast for Ryoku, another girl who appears in the clip alongside the protagonist Rin, has not yet been announced.