From Yomi Hirasaka's Twitter account it has been revealed that volume 14 of the light novel A Sister's All You Need (Imouto Sae Ireba Ii) will have a "surprise project".
Let's remember that volume 14 is the end of the series and will be on sale on February 18th.
The novel was first published in 2015 and was illustrated by Kantoku. And in October 2017, the series got an adaptation to the anime, which can be seen on the Crunchyroll platform.
Synopsis:
Itsuki Hashima is a young novelist whose dream is to one day create the ideal little sister, but this strange character is not alone in his eccentricities. Around him we will find a genius writer madly in love, a college classmate who cares about him, a sadomasochistic accountant who loves to torture others with taxes and even the staff of the publishing house where he works - all for the ideal little sister!
Source: ANN