There have been numerous supplemental stories written by Yoshihara-sensei available in Japan as extras for purchasing either 2012 audio remake CDs, anime remake or the Chara releases. Some of these have been translated by fans and their curated links appear below. All efforts have been made to “give credit where credit is due” and no infringement is intended. All rights belong to the original author.
Kizu (Wound)
Night of Disgrace
Illusion Night