Pre-Lunatics is a short manga by Syuji Takeya included with the Deluxe Edition of the 2016 release of The Silver Case. It depicts the events occurring shortly before and at the very beginning of case#0:lunatics, with the last few pages of the comic matching the beginning of the case. The case is known as "Pre-Lunatic" on the History of 24th Ward timeline.
[https://www.believeinthe.net/wiki/Pre-Lunatics]