This DLC is Chapter 4, " Wings of Blood," of The Grade 5B Case Files. Recently, the anime Detective Girl Alice finally welcomed the return of Wings of Blood, much to the delight of fans of the character.

But that's not the only reason Holmlyn is in such a good mood today. After buying a new pair of scissors, she finally completed the new paper airplane design she had been working on. Just as this pleasant day is about to come to an end and she's getting ready to head home to watch the latest episode, she discovers a calling card from Wings of Blood inside her desk!

Most students have already left school by then, while only a handful of classmates and teachers remain on campus. None of them seem to realize that Wings of Blood has already gracefully descended onto the school's rooftop...

Holmlyn: You can stop hiding, Wings of Blood. I already know who you really are.