Just some oneshots Takano Saku published on her pixiv last year. They were published before the series and only have a loose connection to the events in the official manga.
title: Vampire-chan × Junior-chan
author: Takano Saku
original work published from: 2016-10-11 to 2016-12-25
proofread: Altair, A916
QC: bronx819, Altair, A916 (aka Team BadAss⑨)