(Note: Some DVD releases include a "Bonus Episode 0" – a prologue showing Ryoji’s first victim, which is 15 minutes long and serves as backstory.)

I'm assuming you're referring to the anime episode "Souryo to Majiwaru Shikiyoku no Yoru ni" (which roughly translates to "The Night of the Shiki and the Maji Mixing"). However, I need more information about the anime it's from, as there are multiple anime with similar titles.

* Based on Maomi Leon's manga. A woman reunites with her first love at a class reunion. She discovers that Kujou has taken over hi... Souryo To Majiwaru Shikiyoku No Yoru Ni

The popularity of the anime helped boost the profile of the original manga, demonstrating the effectiveness of the short-form adaptation strategy.